Instagram’s own photo collage creator Layout is now available on Android, after launching on iOS only back in March. The app allows users to combine multiple pictures from their camera roll (or direct from the camera itself) to create a single composite image with a square aspect ratio suitable for sharing on Instagram.
The app allow you to customize the layout, using a number of pre-defined templates and then tweaking them as desired. You can fix and mirror images, replace them with others, and adjust the borders between them. You can share the results both to your camera roll, and to Instagram and other social destinations.
It’s free, and should work with most Android devices running version 4.1 and higher.