We love this hanging shelf made of only 3 elements: a (painted) board, suede or leather lacing, wall hooks. We imaging how to make it: drill holes in the board…thread the lacing through them and knot…affix the hooks into the wall (in a stud!) and hang. (A carpenter friend has told us that 30 inches is about the biggest span for loading up a shelf without it bowing.)
You’ll find more hanging shelf iterations here. These are some favorites.:

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Top via SF Girl by Bay; photo Martin Sølyst for Bolig Magazine