A couple of points to consider: I always load my reel up backwards at first, by putting the fly line on first. In this way I'll know exactly how much backing will fill the reel. Then I remove it all from the spool, turn it around & load the reel up with the backing first, so it's all going in the right direction.
Also, I don't like to use the loop connections when attaching my leader to my fly line. I know it's silly, but I prefer the added security of a nail knot there. Plus, a nail knot is much thinner than the loops & will slip through the small tip top on a fly rod easier. I don't want my line & leader connection getting stuck in the tip top!!
One last point on the nail knot: the trick to tie this knot shown in the video is fantastic - using a straight piece of metal, etc & a loop. However, they are not absolutely essential to tie this knot. Back in the day (if I may use that phrase) we never used any tools to tie the nail knot. Yes, this trick makes it a million times easier, but before I knew about it I just tied the nail knot without any loops or other tools & you can too if you need to do this along the stream. Practice makes perfect, so don't fear the nail knot!
Backing to reel; fly line to backing; leader to fly line - here are the knots you'll need to get your fly reel all rigged up!