In my opinion, the real trick to these building blocks is to choose a wide variety of blocks. In our house, we have a ridiculous number of building blocks, entirely thrifted, hand-made, or bought as unfinished scrap, so we chose our set from our stash. If you don’t have a large enough stash of blocks to be able to sacrifice several for chalkboard blocks, then I highly recommend checking out a lumber yard for scraps or a company that makes wooden blocks, like Barclay Blocks–I’ve twice purchased sets of their free(ish) unfinished scrap blocks, and been really pleased with what I received each time.
Whether or not the blocks that you’ve chosen are already painted or varnished, or are left unfinished, first give them a look-over, making sure that they’re clean and dry and any sharp edges are sanded down, then paint them all over with primer.
Next >> Keep it Dry!