After removing the Boot Camp partition:

frank@drou-2:~$ diskutil list
/dev/disk0 (internal, physical):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            *4.0 TB   disk0
  1:            EFI â ¨EFIâ ©           209.7 MB  disk0s1
          (free space)             2.0 TB   -
  2:         Apple_APFS â ¨Container disk1â ©     2.0 TB   disk0s2

/dev/disk1 (synthesized):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   APFS Container Scheme -           +2.0 TB   disk1
                 Physical Store disk0s2
  1:        APFS Volume â ¨Macintosh HD - Dataâ ©   359.7 GB  disk1s1
  2:        APFS Volume â ¨Prebootâ ©         292.9 MB  disk1s2
  3:        APFS Volume â ¨Recoveryâ ©        613.8 MB  disk1s3
  4:        APFS Volume â ¨VMâ ©           2.1 GB   disk1s4

  5:        APFS Volume â ¨Macintosh HDâ ©      15.1 GB  disk1s5
  6:       APFS Snapshot â ¨com.apple.os.update-...â © 15.1 GB  disk1s5s1

/dev/disk3 (disk image):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            +950.0 GB  disk3
  1:            EFI â ¨EFIâ ©           209.7 MB  disk3s1
  2:         Apple_HFS â ¨Time Machine Backupsâ ©  949.7 GB  disk3s2

Add a new partition named NewAPFS:

frank@drou-2:~$ diskutil addpartition disk0s1 apfs NewAPFS 0
The new partition to be added will be of a filesystem personality of APFS apfs APFS 7C3457EF-0000-11AA-AA11-00306543ECAC
The new partition will be added following disk0s1
Started partitioning on disk0
Modifying partition map
Mounting disk
Finished partitioning on disk0

After adding a new partition:

frank@drou-2:~$ diskutil list
/dev/disk0 (internal, physical):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            *4.0 TB   disk0
  1:            EFI â ¨EFIâ ©           209.7 MB  disk0s1
  2:         Apple_APFS â ¨Container disk4â ©     2.0 TB   disk0s4
  3:         Apple_APFS â ¨Container disk1â ©     2.0 TB   disk0s2

/dev/disk1 (synthesized):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   APFS Container Scheme -           +2.0 TB   disk1
                 Physical Store disk0s2
  1:        APFS Volume â ¨Macintosh HD - Dataâ ©   359.7 GB  disk1s1
  2:        APFS Volume â ¨Prebootâ ©         292.9 MB  disk1s2

  3:        APFS Volume â ¨Recoveryâ ©        613.8 MB  disk1s3
  4:        APFS Volume â ¨VMâ ©           2.1 GB   disk1s4
  5:        APFS Volume â ¨Macintosh HDâ ©      15.1 GB  disk1s5
  6:       APFS Snapshot â ¨com.apple.os.update-...â © 15.1 GB  disk1s5s1

/dev/disk3 (disk image):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            +950.0 GB  disk3
  1:            EFI â ¨EFIâ ©           209.7 MB  disk3s1
  2:         Apple_HFS â ¨Time Machine Backupsâ ©  949.7 GB  disk3s2

/dev/disk4 (synthesized):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   APFS Container Scheme -           +2.0 TB   disk4
                 Physical Store disk0s4
  1:        APFS Volume â ¨NewAPFSâ ©         806.9 KB  disk4s1

After using Boot Camp Assistant:

frank@drou-2:~$ diskutil list
/dev/disk0 (internal, physical):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            *4.0 TB   disk0
  1:            EFI â ¨EFIâ ©           209.7 MB  disk0s1
  2:         Apple_APFS â ¨Container disk2â ©     50.0 GB  disk0s2
  3:    Microsoft Basic Data â ¨OSXRESERVEDâ ©       10.0 GB  disk0s3
  4:    Microsoft Basic Data â ¨BOOTCAMPâ ©        1.9 TB   disk0s4
  5:         Apple_APFS â ¨Container disk1â ©     2.0 TB   disk0s5

/dev/disk1 (synthesized):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   APFS Container Scheme -           +2.0 TB   disk1
                 Physical Store disk0s5
  1:        APFS Volume â ¨Macintosh HD - Dataâ ©   369.6 GB  disk1s1

  2:        APFS Volume â ¨Prebootâ ©         292.9 MB  disk1s2
  3:        APFS Volume â ¨Recoveryâ ©        613.8 MB  disk1s3
  4:        APFS Volume â ¨VMâ ©           2.1 GB   disk1s4
  5:        APFS Volume â ¨Macintosh HDâ ©      15.1 GB  disk1s5
  6:       APFS Snapshot â ¨com.apple.os.update-...â © 15.1 GB  disk1s5s1

/dev/disk2 (synthesized):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   APFS Container Scheme -           +50.0 GB  disk2
                 Physical Store disk0s2
  1:        APFS Volume â ¨NewAPFSâ ©         938.0 KB  disk2s1

/dev/disk3 (external, physical):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   FDisk_partition_scheme            *7.8 GB   disk3
  1:       Windows_FAT_32 â ¨CHK-HLLâ ©         7.8 GB   disk3s1

/dev/disk4 (disk image):
  #:            TYPE NAME          SIZE    IDENTIFIER
  0:   GUID_partition_scheme            +2.0 TB   disk4
  1:            EFI â ¨EFIâ ©           209.7 MB  disk4s1
  2:         Apple_HFS â ¨Time Machine Backupsâ ©  2.0 TB   disk4s2