You go to route 111, above the desert, and there will be a guy standing alone. Talk to him, and he will give you a tm. It will be Secret Power. Teach it to one of your Pokémon, preferably a weak one, so you can have your stronger Pokémon know better moves. Walk up to a tree or bush, and it will say "Would You Like To Use Secret Power?" Select yes and you will make a secret base.
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If you have or have taught a pokemon the move Secret Power, you can use it on those vine trees, notches in cave walls, and big bushes to turn them into a secret base.
There is no move tutors AT ALL in Sapphire/ruby.
HM Rock Climb
Rock Climb is not a move in the game. It wasn't a move until Diamond/Pearl/Platinum, which came out after FireRed.
Use the move Secret Power on certain trees and climb the vine that falls down. Use the move Secret Power on certain trees and climb the vine that falls down.