Cut 15 top boards 5 ft. long and rip them to 3 in. wide with a table saw so the top will glue up flat without the typical rounded edges of 2x4s. For the leg slot, cut two of the top boards into three pieces: a 39-in. middle piece and two 7-in. end pieces. Glue and screw the top together, one board at a time, with 3-in. deck screws, keeping the ripped edge facing up and level with the adjoining boards. Use a corded drill so there’s plenty of oomph to drive each screw below the surface. Note that the third glue-up from each end is where each leg notch is inserted. You can also create a nifty tool tray in the top by notching the three top pieces with a jigsaw. Clamp every 8 in. or so before driving in the 3-in.deck screws. Predrill the screw holes near the ends to prevent splitting. When you’re screwing on the 7-in. long 2x4s to create the leg slots, use a scrap piece of 2×4 as a spacer.
This is a great project if you carefully consider your needs first. I left out the vise and tracks, but had no problem hand picking good 2x4 stock at the big box stores. I did use maple on the top sides in case I ever decided to add tracks, but it was not a budget buster by any means. The cabinet and drawers were a first for me and a great learning experience. I also added retractable casters so I can easily move the workbench around my shop. Love the workbench!