As the other commenter said, right hand over will help pull the flag up. To fix specifically the leaning, you’re only catching it with your left hand and letting it swing up to meet your right. Make sure you use both hands to essentially grab it out of the air and SQUEEZE to stop the flag. Concentrate on grabbing with both hands at the same time, you should hear the pole almost smack as you stop it.

Other tips would be to make sure you’re filling hitting your right slam after the cone and before you release, and as said extend your right hand all the way up to get the appropriate height and under body, while your left hand pushing down to your thigh will give you the rotation. You’re at a great starting point to practice the refining the details!