Another very safe cliff spot. All the hidding spots in the Relay cliff are very strong if the zone is at your South in Swamps since no team should have a line of sight on you.

To access this spot, you will need an Octane. Roughly place a Launch Pad where indicated in the screenshot below and super jump: press your jump key right after you hit the Launch Pad and be ready to air control and climb when you hit the cliff. Once you are there, you can lock yourself in the crouched position. Try to have all your team members at the same place so you are less likely to be noticed.

The only danger can come from Relay itself so either get there early when you 100% cleared the area or when the zone is at your South. Just make sure that you can leave the cliff early enough in order to reach the zone without taking too much damage, especially if the game is close from an end.