This will produce one shelf and six brackets, of which you will only use five. It will also produce 4-inch wide cleat material. I show two rip cuts for the cleats. Glue and screw these together ...

Assemble the 2x4s as shown , using five-inch corner braces and 1/4-inch x 1-inch hex head lag screws (drill pilot holes first ...

There’s a workbench in there somewhere, but it would take a long time to get to it. These tools and cases need to be be moved off the bench, but stored in an easy-to-reach location. There is ...

Glue the two legs to the bottom of what will be the countertop support, then pre-drill holes for and fasten with two screws ...