My favorite provably fair slot is the one on Stake, it is the Scarab spin slot (egyptian themed).
Just for your information, and perhaps can be added on the list. There are still some provably fair slot out there such as:
1. The Fruitsler slot at Bitsler
2. Fruit Slot at Coinroyale.
3. Slot game at Crypto.games

You may try it first if you havent, but I think the Fruitsler slot by Bitsler is the best compared to the other last two.