This is a left and right side base for the DeWALT TSTAK II FLAT TOP tool box (DWST17807). It conforms to the bottom of the tool box so you can fill it with Gridfinity-based containers. I used a magnet base so that the containers won't flop around if you carry it somewhere.
You need to print both (left and right) to have a complete base. These are quite large, so you need a decent sized print bed, but you could also slice these in half and print each side as 2 pieces. Each half is a 4x6 grid of gridfinity slots giving a total capacity of 8x6 = 48 slots.
Add a question if you're interested in the DeWALT yellow colored filament I used if interested.
The author marked this model as their own original creation.