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.