Form four planks of 35-inch 2-by-2 lumber and four planks of 14-inch 2-by-2 lumber into two rectangular frames. The ends of the 14-inch pieces should abut the inside of the 35-inch pieces to make the corners. Slot a third piece of 14-inch lumber in the center of each frame for an extra support plank. Glue the frames together, checking with a carpenter's square that all the angles are square.
Drill two countersunk pilot holes through the side of the frames into the abutting ends of each 14-inch lumber piece and secure the frames together with 2 5/8-inch wood screws. Set one frame aside for the moment.
Lay the remaining frame flat on a work surface. Evenly space 5 planks of 1-by-3 lumber that measure 35 inches over the top of the frame and secure them to the frame with 1-5/8-inch wood screws driven through each plank into the three 14-inch support planks of the frame. This is the shelf of the kitchen cart.
Turn the shelf on its side and position the other frame on its side, 20 inches above it. Place two planks of 2-by-3 lumber measuring 28 inches (the cart legs) over the sides of the frames, 2 inches in from each side, and with the top of the legs flush with the top of the top frame. There will be 8 inches between the shelf frame and the bottom of the legs.
Drill two countersunk pilot holes through the legs into the side of each frame and secure the legs in place with 3-inch lag bolts. Turn the frames over so that the other side is exposed and attach two more legs in the same manner.
Lay a sheet of 1-1/2-inch-thick lumber measuring 22-by-39 inches (the cart top) flat on a work surface. Apply glue to the top side of the top frame, then invert the cart over the cart top, so the legs are in the air. Adjust the cart so that the top frame is 2 inches from each side of the cart top.
Drill two countersunk pilot holes through the underside of each 14-inch support plank of the top frame into the underside of the cart top and secure with 2 5/8-inch wood screws. Drive four evenly-spaced screws through the underside of the sides of the top frame into the cart top as well.
Place a caster in the end of each leg while the cart is still upside down and secure the casters in place with the screws that accompany the casters. Turn the cart back up the right way, then finish it with the desired wood finish. If you plan to use the cart as mostly decorative or for storage, then paint, varnish or lacquer are fine. If you want to use the top of the cart for cutting, a wax polish or oil finish is better. You can also combine finishes, so that the top is waxed or oil and the rest of the cart is painted or varnished.