If you have it, you can usually reference your owners manual. Sometimes they have a fuse and relay layout page. Check the inside of the fuse box cover for a layout as well. I'm not sure on your Corolla but it may be an in line relay that plugs into the harness itself under the dash.
You are probably looking for a small (about the size of a quarter) round metallic plug in relay.
If it is the flasher relay, just replace it with the normal relay. Some folks think that if a heavy duty is offered that would be better, but it usually is not. It has a thicker bi metal spring (for accessory wire harnesses like a trailer) that takes more amperage and thus more time to cycle. Your flashers will usually flash much slower if you use one.