I use Pocket Paint/Paintroid: https://f-droid.org/en/packages/org.catrobat.paintroid/

You can easily do it in Photopea. It works in the browser on mobile and computer - no download or installation needed! If you’re familiar with Photoshop, you’ll have no problem with it.

This app seems to do the trick: https://www.f-droid.org/en/packages/com.burhanrashid52.photoediting/

Some screenshot/screen-capturers does that. Like ScreenshotTile