Step 4: Finished!
Congrats! Now you can screw the whole box you've just made underneath your workbench/table, and fit in your drawer(s)!
For the finishing touch: I've made little "L"'s and "I"'s in the back for my toolbox, so it won't move around when I pull it out or open it.
Big thanks for reading my (very first!) instructable! Let me know if you've made one for yourself!