It would be easy in a 3d program, but I’m sure Easel can do it with a little manipulation. I drew my bottom rectangle and made a cylinder on top. Then I moved the cylinder half way down into the rectangle and split it. Lastly I deleted the parts that I didn’t need of the cylinder.
There are also roundnose cove bits that would create a rounded bottom slot.
Use the search feature with the word poker as I did: