What is really important is:
- to identify a corner-edge pair to assemble,
- mentally figure out what are the moves you need to put the pair in an "insertable" position (through RUR', RU'R' or R'FRF')
- execute the pair positioning and insert it without looking at it
- identify the next pair as your fingers insert the current one (the infamous and difficult look-ahead)
Three things to add:
- with practice you will start to acquire muscle memory for many given pair configuration
- you will also learn how to do this from any 4 angles, not just the Right-Front location
- at some point you should also look at some EO (edge orientation) discussions, that will guide you on minimizing the number of cube rotation (re-grip) you need to do.
You should also aim at 7 moves in average for the cross and each of the pairs, at total of 35 moves for F2L.
Last and most important: when learning F2L it is not about the time you achieve. It is about the number of rotations you can in a row without stopping or slowing. Even if you start at 3 seconds per rotation and finish F2L without missing a beat you are on the right track. Then slowly try to increase your tps (turn per second rate). Day after day. Week after week. Or if you're like me, month after month
The cross should be part of the process, as you should it entirely from memory (after inspection) as you look for your first pair and anticipate where it will be at the end of the cross.
Don't worry, your time will improve. Good luck.
