Ralph, at Accidental Woodworker, pushed me in the direction of a captured bottom today. I had been leaning that way, but his comment tipped me over. So tonight I set about squaring up a piece of red oak. I chose 1/4″ as the final thickness since that is the smallest groove I can currently make and also to capture all of the bottom rather than just a lip. The groove will be 3/16″ in depth, allowing for 1/8″ of board and a gap of 1/16″ on each side. The bottom will float in the groove and I hope I’ve allowed enough for seasonal changes.
Once I had the bottom squared and correctly sized, I laid out the grooves on each piece measuring referencing from the top of each piece. Which reminds me, I need to visually inspect the groove on each piece to make sure they line up from piece to piece. I don’t want to repeat the mistake I made on the tool chest drawer. Below is a pic of the sides and bottom. If you look closely, you can see the groove lay out lines. Stay warm and be safe.