Cut off a 21-in. long board for the shelves, rip it in the middle to make two shelves, and cut 45-degree bevels on the two long front edges with a router or table saw.
Turn a single 3-ft. long, 1×12 hardwood board into some small shelves to organize a desktop or counter. Cut off a 21-in. long board for the shelves, rip it in the middle to make two shelves, and cut 45-degree bevels on the two long front edges with a router or table saw. Bevel the ends of the other board, cut dadoes — grooves cut into the wood with a router or a table saw with a dado blade — cross-wise (cut a dado on scrap and test-fit the shelves first!). Then cut it into four narrower boards, two at 1-3/8 in. wide and two at 4 in.