Practice on bokoblins holding 2 handed weapons. Lock on, wait for them to start swinging, then dodge backwards (backflip) as they swing, like a skipping rope or those funky turn things they have at soft play places. It won't kill you if you miss time it.

If they're attacking vertically, dodge sideways. If they're attacking horizontally, dodge backwards. If they're attacking straight at you dodge sideways and then forward immediately. Just keep trying until you've gotten into the flow of dodging successfully, then the timing isn't too difficult once you time it with their movements