Preheat oven to 400. Cut the tops from the peppers and halve them lengthwise. Remove the veins and seeds; brush the skins with olive oil and lay out flat on a cookie sheet with the skin side up. Bake at 400 or broil 5-6 inches from the top element/burner in your oven until the skins are wrinkled but not charred, 10-20 minutes. Remove and stack peppers to steam in a pile for 15 minutes.
At this point you can rub off the skins with your hand or the help of a paper towel. A cold water bath can help this process but washes away a lot of flavor.
These flat peppers are easy to freeze by stacking them with wax paper between each layer and slipping them into ziplocks. Remove as much air as possible and freeze flat.