Reload OS on different internal hard drive

I have a Power Mac G4 (Mirror Front) and am currently running Leopard (10.5.8) on it. It came with a 20 GB HD and I have added a 250 GB HD to it. What I would like to do is transfer the OS over to the 250 GB drive. I've seen some posts that talk about cloning software. Is that the best way or could I some how reload the OS on the bigger drive and remove or make the smaller drive a slave.

thanks!