What ever skill's you can work the best. I being a carpenter-engineer use mdf board (dense stuff they build speakerboxes out of) or if you have a ac/buddy that can get you some insulation board that they use for ducking and plantuims. What ever you use make sure you caulk the inside. Start with square shape box on inside alternat the opening from side to side three or four time and that will work for you. Hope that helps. Later