I haven't tried this method, but here's what I would do. I'd line a square baking pan with parchment paper, then press the sugar down flat using the back of a measuring cup to make it even. Then, use a knife or bench scraper to form cube-like shapes by cutting the compressed sugar into a grid. Bake or dry like normal! I haven't tested this, so I'm not sure how it will work, but this is what I'd try. You can also individually compress each cube, but that would take a very long time! It's much, much easier and faster to grab a mold. They don't have to be cubes, either. I've found little truffle molds for $1 at craft stores before.