lock ipad screen for backup

Assuming you have turned on iCloud backup in Settings > Your Name, Apple ID, iCloud, etc. Plug your iPad into power, with Wifi connected, then simply tap the power button once to lock your screen and your iPad will backup to iCloud.

Most of us, have iCloud backup enable, and while connected to Wifi, plug our iPad's in to charge while we sleep at nigh and as long as the screen is locked (meaning it's not on), at some point during the night, the iPad will backup on its own.