Pull the edge of the freezer door gasket back with your thumb to expose the mounting flange and screws. Remove the screws from the flange with a screwdriver; freezer gasket mounting screws are most commonly of Phillips head design.
Peal the freezer door gasket off the metal mounting flange, with your fingers, and inspect the entire gasket for damage. Clean a gasket that passes inspection; replace a gasket showing any signs of rips, tears or cracks.
Soak the gasket in a sink of warm soapy water for 30 minutes. Gently scrub the gasket with a nylon bristled brush, working the brush thoroughly through all gasket creases. Run the gasket under warm water while opening the folds in the gasket with your fingers, rinsing away all debris and soap residue. Wipe the gasket dry with paper towels.
Clean all traces of dirt and food particles from around the edge of the freezer door and fame with a sponge and warm soapy water.
Install a new or clean gasket onto the mounting flange and reattach the flange to the freezer door with the mounting screws and screwdriver.