Copper sulfate is produced industrially by treating copper metal with hot concentrated sulfuric acid or its oxides with dilute sulfuric acid.
Stir copper sulfate into very hot water until no more will dissolve. You can just pour the solution into a jar and wait a few days for crystals to grow, but if you grow a seed crystal, you can get much larger and better-shaped crystals.
Pour a little of the saturated copper sulfate solution into a saucer or shallow dish. Allow it to sit in an undisturbed location for several hours or overnight. Select the best crystal as your 'seed' for growing a large crystal. Scrape the crystal off of the container and tie it to a length of nylon fishing line.