FS drills for 33 stack defense

We do a few drills at my level for our free safety. The main ones we do are backpedal and break drills. We work on breaking at different angles and teaching them how to plant their feet appropriately (t plant). We also do these drills with open field tackling.

Another drill that I like for a cover 1 or cover 3 team is to have the safety backpedal between the hashes and send receivers up each hash. The safety is responsible for watching the QB's shoulders to determine which way he's aiming when his hand breaks from the ball. When it does he breaks toward that hash and makes a play on the ball, either picking it or stripping it from the receiver.

One drill that really improved my safeties ability to play the ball was our pick drill. It is similar to the drill above. You line up two safeties beside each other but with 10 yards between them. On the snap, they must backpedal. After a couple seconds, the coach will lob a ball in between the two players, the players are not allowed to break their backpedal until the ball is in the air. The first thing the safeties do is go for the interception, but when they realize they can't get it, they strip the ball. What this does is it teaches them to strip if they can't pick it, but it also teaches them that if they have a chance at an interception, how to hold onto the ball when somebody is trying to strip it. If one gets the interception, the other player does 10 push ups. If a player strips it, the one who had it stripped does 5 push ups. Hope these drills are what you had in mind!