l know this question might seem a little silly, but how do you find rocks?

Just go around and explore the locations

You can get rocks anywhere by exploring,  but I'd recommend going to the riverside. There are no enemies there and you can get plenty of rocks.

Daylight: Riversider

Night: Go to one of the two Slime-Forest and kill Ghosts. You need to kill tons of ghost for ectoplasma (several fetchquest) anyway.