Just after unsuccessful native BC way, both efi partitions displays very similar structure:
/Volumes/efissd/
/Volumes/efissd//EFI
/Volumes/efissd//EFI/APPLE
/Volumes/efissd//EFI/APPLE/EXTENSIONS
/Volumes/efissd//EFI/APPLE/EXTENSIONS/Firmware.scap
/Volumes/efissd//EFI/APPLE/CACHES
/Volumes/efissd//EFI/APPLE/CACHES/CAFEBEEF
/Volumes/efissd//.Spotlight-V100
/Volumes/efissd//.Spotlight-V100/Store-V2
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/p sid.db
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/t mp.SnowLeopard
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/t mp.Lion
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/L ion.created
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/t mp.Cab
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/C ab.created
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/i ndexState
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexHead
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexIds
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexGroups
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexPostings
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexTermIds
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexPositions
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexPositionTable
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexCompactDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexArrays
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .indexUpdates
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .directoryStoreFile
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexHead
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexIds
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexGroups
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexPostings
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexTermIds
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexPositions
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexPositionTable
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexCompactDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexArrays
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.indexUpdates
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.directoryStoreFile
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/s tore.db
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/. store.db
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/r everseDirectoryStore
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/t mp.spotlight.state
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournalAttr.1
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/s tore_generation
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.corespotlight
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.live
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.live_system
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.live_user
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.live_priority
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.assisted_import_pre
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.assisted_import_post
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.health_check
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.migration
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.migration_secondchance
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournalExclusion
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.scan
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/j ournals.scan/retire.8
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/s hutdown_time
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/r everseDirectoryStore.shadow
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .shadowIndexHead
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .directoryStoreFile.shadow
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/0 .shadowIndexGroups
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexHead
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexTermIds
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexPositionTable
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexArrays
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexCompactDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexDirectory
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.directoryStoreFile.shadow
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/l ive.0.shadowIndexGroups
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/s tore.updates
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/r everseStore.updates
/Volumes/efissd//.Spotlight-V100/Store-V2/A6E6420D-CABE-4E5F-B366-80F1142AC6AB/t mp.spotlight.loc
/Volumes/efissd//.Spotlight-V100/Store-V1
/Volumes/efissd//.Spotlight-V100/Store-V1/VolumeConfig.plist
/Volumes/efissd//.Spotlight-V100/VolumeConfiguration.plist
/Volumes/efissd//.fseventsd
/Volumes/efissd//.fseventsd/fseventsd-uuid
manually using EFI boot... do you mean use BC only to create EFI boot flash-key windows installer, and create 1) free space using diskutil 2) fat partition using diskutil ?