making shallow cut outs for puzzle pieces

So I have a good thought for a project and am hoping that all you experts can help me make it a reality. I’d like to make a childrens puzzle board with pieces that can be slid into place then picked up and removed. Basically just like the ones you’d normally see- a big flat board (maybe 1 square foot big) with shallow cut outs(indentations) that kids place shaped pieces into and back out of. For example I often see ones that have themes such as numbers, letters, animals etc…

How would one make shallow cut outs/routed out designs on a board? I”m thinking REALLY shallow, like somewhere around 1/16 inch or just enough to catch a 1/4 thick puzzle piece that would then still leave plenty of room for a childs’ fingers to grab to pick up and out.

Could I make a template out of mdf then use a tray/dish carver bit to route out my shallow shapes? All these bits that I’ve seen though have a roundover. Are there any that make a square edge at the bottom? Thanks and happy crafting! Cheers, Justin

-- Justin, Smiling Tree Toys, http://www.smilingtreetoys.etsy.com