I stumbled across this product, while not strictly a DIY project, it's certainly DIYable. All you need are some wooden offcuts and a saw, choose your angle and cut a groove 70% of the way through, presto, instant photo block, perfect for showcasing your printing Instagrams.
If you'd prefer to skip the DIY option, they're available to purchase directly from link below.
Wood Block + Prints via Artifact Uprising
Material : wood
Techniques : woodworking
Decor Element : accessories