Assemble the Top Brace
Cut 1-by-6-inch-by-10-foot lumber to the required sizes for the top brace with a saw. Measure the lumber with a tape measure and cut one piece that is 34 3/8 inches in length. Cut a 45 degree angle on both ends. This piece will be the front of the brace. Cut one piece that is 32 7/8 inches in length for the back of the brace. Cut two pieces that are 19 inches in length. Cut a 45 degree angle on one end of each 19-inch-long board. These will be the sides of the top brace.
Connect a side to the front of the brace. Join the two ends with 45 degree angles. Secure with a screwdriver and wood screws. Repeat to connect the other side of the brace.
Attach the back of the brace. Secure the ends to the side pieces with wood screws. This is the completed top brace.
Assemble the Top Panel
Cut 3/4-inch plywood with a saw. Measure the plywood and cut a 38 5/8-by-20 1/2-inch piece. Use sandpaper to sand all four edges until smooth. This is the top panel of the desk.
Measure the back of the top brace and the top panel. Mark the center with a pencil. Align the mark on the top panel with the mark on the top brace. The back of the top panel should be flush with the back of the top brace. There will be a slight overhang on the front and sides.
Attach the top panel to the top brace with wood screws.
Complete the Desk
Use a saw to cut four legs that are 28 ½ inches in length from 2-by-4-inch-by-10-foot lumber.
Cut three bottom braces from 1-by-6-inch lumber. Cut one piece that is 34 3/8 inches in length. Cut a 45 degree angle on each end. This will be the back of the bottom brace. Cut two pieces that are 19 inches in length and cut a 45 degree angle on one end of each piece. These pieces will be the sides of the bottom brace.
Attach the back and sides of the bottom brace. Align the 45 degree angles and secure with wood screws. Measure 2 ½ inches from the bottom of a leg and mark it with a pencil. Place the leg in the corner of the bottom brace. Place the bottom edge of the brace on the mark on the leg and secure with wood screws. Repeat to attach a second leg. These are the back legs.
Place the top of the back legs into the back corners on the top brace. The back of the top brace is flush with the top panel. Secure the legs to the brace with screws.
Place a third leg into the front corner of the top brace and secure with wood screws. Attach the leg to the bottom brace and secure with screws. Repeat to attach the fourth leg. Stain or paint the desk, as desired.