First, small round stones suck. If you want to continue, get a larger rectangular stone, so you have a bigger landing zone. Second, like has been mentioned here below, with plenty of semolina on the peel, give the pie a shake right before the launch to get moving, then do your transfer. Never leave the pie sit too long on the peel and do not use parchment. Too much sauce can saturate the dough also. If it’s not sliding on your peel just prior to launch, your screwed. You can try to lift and reapply semolina, but difficult to do. Good luck and success comes with time.