Basically, you pan the camera (the overworld camera! NOT the new camera feature) with L and R on an area where a monster spawns. To be more specific, near the Riverside Church going down to the river's bank where Metal Slime spawn, just when you enter the brown bank a monster should either to your left or right depending on where your camera was facing. Stand in between an area where they tend to spawn then pan it Left and Right with L and R. Whenever you look away and look again, a new monster should spawn each time. Keep doing this until a Metal Slime spawns then chase it making sure your camera is facing it or else there's a chance it'll disappear. Don't worry about not being fast enough to chase it, it'll tire out eventually and stop along the path, it won't disappear at the end like the monsters in DQVII. The Ruined Abbey works too but I find the poison pools to be annoying. This should generally work with any monster that spawns so it's also good for monster defeat collection if you're after specific monsters. This exploit works best with an area that's narrow so you can just stand still and pan Left and Right.