Lay two planks of 30-inch, 2-by-2 lumber flat on your work table, parallel with 16 inches between them.
Evenly space four planks of 16-inch, 2-by-2 lumber between the two parallel 30-inch planks, with the ends of the 16-inch planks abutting the inside edges of the two 30-inch planks. The two outer 16-inch planks should be flush with the ends of the 30-inch planks, creating a rectangle shape.
Secure the 16-inch planks in place with two 2-3/4-inch wood screws driven through the sides of the 30-inch planks into each end of all four 16-inch planks. This is the apron frame of the desk. The legs will be attached at each corner of the apron frame, and the frame attached to the underside of the desktop.
Insert a 28-inch, 4-by-4 lumber plank into each corner of the desk apron frame. These are the legs for the desk.
Secure the desk to the apron frame with four 3-inch wood screws driven through each corner of the apron frame into the legs; two screws for each side of the corner, making four screws per leg.
Place a 16-inch plank of 1-by-4 lumber between a pair or legs, 10 inches down from the end of the legs and parallel with the 16-inch planks of the apron frame. These are the stretchers for the desk legs.
Secure the stretchers in place with two 2-3/4-inch screws through the stretcher ends into each leg.
Apply wood glue to the 1-inch edge of one long side of a plank of 36-inch, 1-by-12 lumber. Lay it flat on the work surface. Abut a second plank of 36-inch, 1-by-12 lumber alongside the glued edge and press the two planks together. This will form a single plank, 24-by-36 inches, which is the desktop.
Clamp the desktop planks together with an F-clamp and let the glue dry.
Apply leather adhesive to the back of a piece of 23-by-35-inch leather using an ink roller, then center the leather glue-side down on the desktop. There should be 1/2-inch gap all around between the edge of the desktop and the edge of the leather.
Press the leather firmly onto the desktop, using rags to avoid scratching the leather. Leave for the time recommended by the leather adhesive manufacturer for the leather to firmly bond to the desktop.
Lay down protective rags on your work table and place the desktop leather-side-down on top.
Center the apron frame over the underside of the desktop. The legs should be up in the air at this point.
Secure the apron frame to the underside of the desktop with four evenly-spaced 2-3/4-inch screws through the 16-inch planks of the apron frame into the underside of the desktop, and six evenly-spaced 2-3/4-inch wood screws through the 30-inch planks of the apron frame into the underside of the desktop.
Turn the desk over so that it is standing on the legs.