Cut the Edge Trim
Using a circular saw, rip four 1 ½-inch strips from one of the boards (this will be the edge trim). Two of the strips should measure the length of the table and two should measure the width.
Trim the Boards to Length
Cut 1½-inches off the length of the other three boards. If you are mitering your edging, this will allow the original length to turn and wrap the corners.
Connect the Boards
Clamp the three boards together facedown.
Attach Battens to the Underside
Cut two battens (one for either end of the table) from 1x boards that are wide enough to accommodate the hairpin-leg base. If desired, add a third, thinner batten in the center of the table for support. Secure each batten to the tabletop with six screws, two for each tabletop board.
Trim Out the Edges
Glue the edge trim to the tabletop so that it lies flush with the three boards when they are rightside up, then secure the trim using a nail gun.
Wax the Edge Trim
If needed, coat the trim with paste wax that matches the finish of your tabletop. Let dry.
Mark the Legs' Positions
Flip the tabletop back over so that you can see its underside. Position the hairpin legs in each of the table's four corners; trace their inner angle with a pencil.
Attach the Legs
Use the lines you just drew as a guide for determining how far to space the legs from the table's edge. Screw the legs into the battens.