Step 1: Design
Step 2: Materials and Tools
Much of the design was borne out of the fact that I had a lot of bits of plywood lying around after renovating our basement - the previous owners of our house had a thing for plywood cupboard doors. I also had various lumber offcuts and a pair of 2" caster wheels. I bought a pair of 24" full extension drawer slides. If you wanted to make this table from scratch, a 4' x 8' sheet of 1/2" plywood and an 8' length of 2 x 4 ought to see you right, so it'll cost you ~$65 for everything. You'll also need wood glue, nails and paint.
I used a lot of power tools. Mitre saw, bench saw, circular saw, jigsaw, orbital sander, brad nailer and router all got a workout. You could do everything with a circular saw, hammer and some elbow grease, but it would take a lot longer. It took two afternoons to design, cut and assemble, and a few evenings to paint.
Step 3: Build Table Top and Gutter
I had design constraints due to the sizes of the bits of plywood I had. The biggest piece was 850 x 800 mm, and the slide was 650 mm long, so the table top ended up 850 x 650 mm. I made it 150 mm deep, because that looked about right. Both the base and side of the gutter were 90 mm, again, an eyeball choice, and once assembled, made for a trench 90 mm wide and 75 mm deep (because of the way I overlapped the pieces, and because the base of the trench was made using 5/8" plywood). Rip to the right width, cut to length, and assemble with wood glue and a brad nailer. I love my brad nailer - the brads by themselves are feeble, but they make for really fast and precise assembly using wood glue and eliminate the need for clamps. The resulting holes are punched below the surface and are easy to fill. Add end pieces for the gutter to stop bricks falling out.
Step 4: Build Table
Install the slides on the inside of the tabletop, and measure for the table/storage box. I made the side pieces 200 mm high. Assemble into a rectangle of the right size to fit exactly inside the tabletop (don't forget to account for the slides!). Cut some 2 x 2 for legs - I ripped these out of an offcut of 2 x 6, and rounded over the edges with a curved bit in my router. Mine were 600 mm long. Glue and nail into the inside of the box, then add a base.
Step 5: Join Tabletop and Storage Box, and Add Wheeled Legs
Use the slides to join tabletop and storage box. Attach caster wheels to two pieces of 2 x 3 for additional legs, and cut to the right length. Screw down into the top of the legs through the base of the gutter.
Step 6: Add Dividers
Step 7: Storage Box Seats
Step 8: Paint
The seats were similarly treated, the boxes white and the lids orange with construction icons (gears and a wrench) in black. Again, we used stencils and spray paint. Spray paint has the advantage of being easy to apply to stencils, and it is hard-wearing - important in this application given the abuse it's likely to get!
Step 9: Play!
The table is of course equally suitable for other construction toys. The design is pretty flexible - you're only constrained by the lengths of the slides you buy, and these come in up to 36" lengths if you wanted a big table. The table could easily be made as a box rather than with legs if you wanted a cupboard or drawers underneath.
Note: this table is designed to handle stage 6 of Remy Evard's Evolution of Lego Storage. It could probably cope with stages 7-9. For 10-27, you're on your own...