How to Run Block in Flag Football
To begin with, as you approach the line of scrimmage before the play begins, don't get into a standard 3-point stance like you would in normal football. Doing so will make you off-balance when the ball is snapped. Instead, set up in a 2-point stance, bending at the knees and keeping your back straight with a slight arch backwards.
Put your hands behind or back or at your sides. One great idea is to wear pants with side pockets and to put your hands in the pockets to keep yourself from using them illegally.
When the ball is snapped, instead of launching forward like you would in normal football run blocking, move laterally and use quick side-stepping motions to get in the way of the defensive players.
Once you gotten in the way of the player you wish to block, move forward into them, exploding from the hips, and use your weight to push them with your body.
After the play has passed you by, bring your hands to your sides as you would normally have them and run after the play, looking for a potential lateral from the ball-carrier.