You will need these materials:
Approx. 60" of 2" x 4"
Approx. 30" x 30" x 1-1/4" table top from old table or made from laminated plywood
Approx. 24" x 1" dia. wooden dowel or broomstick
8 2" drywall screws
8 #10 washers
Spray paint -- primer and topcoat
Polyurethane or similar
You will need these tools:
Drill and assorted bits
Step 1: Legs!
Chop your raw material to 31-3/4" long at a 5o angle. The angle cuts should be parallel to one another. Connect the corner of one end with the corner of the other, striking a diagonal down the length of the piece. Clamp to a table and cut lengthwise with a circular saw or a bandsaw. I find a circular saw more amenable to straight cuts. Run some 100 grit sandpaper over all the edges and cut faces.
Next, lay out the notches that will connect leg and table top. The exact dimensions are unimportant -- you just want to keep a meaty middle piece to seat firmly in the the depth of the table top. I made mine 2-1/4" by 1-1/2", since that meshes nicely with the dimensions of a standard 2" x 4".
The most important aspect of laying out the notches is that the horizontals are parallel to the top and bottom of the leg, i.e. at that 5o angle. The vertical parts of the notches need to be at 90o angles to the horizontals. All this geometry will ensure that the legs are angled but the table top is flat in the finished product. So, measure down from the top of the leg 1-1/4" inches, or whatever the thickness of your tabletop is, and strike a horizontal. Find the center of that line, then measure 3/4" to either side and pull a vertical. Cut the notches out with a bandsaw or jigsaw.
Last, drill a hole the same diameter as your dowel stock that tangent to the bottom of your notches. This will create the stabilizing bar along the underside of the table, keeping it from rocking side-to-side. A drill press is helpful here, as those holes really need to go straight through the depth of the leg or else they'll end up crooked, and your table may list to one side.
Cut your dowels into 6" sections. Mark a centerline, then measure 3/4" to each side of that line, smear the middle with glue, and tap into the holes in the legs. Let dry.
Sand and slap on a couple of coats of your favorite finish. I put down three coats of a semi-gloss polyurethane, a good, durable, easy-wipe surface in an application that may see its fair share of spills.
Step 2: Toppin' Out
Connect the corners, creating an "X". Measure along the "X", in from the corners, about 6". Center a notch, the exact size of the projecting piece of your legs. Label each notch and each leg, taking into account any small irregularities in dimension, so the table always fits together tightly later.
I taped off my cuts so the laminate didn't chip, but that step isn't necessary if your top is just plain wood. Drill two holes, then cut extremely carefully! The notches need to fit very tightly for maximum stability. Keep to the inside of your layout lines -- you can always enlarge the hole if its too tight, but you can never shrink it . . .
Paint your top with primer, then top coat, then some clear coat for protection.
To assemble, slot the legs in, then drill through the dowels and pop two screws per leg with a washer, which will make it easier to disassemble in the future. Flip it over and relax . . .
When ready to move on, take out the screws and ease the legs out of their slots, leaving five easy pieces!