Step 1: Cut the Holes
Diameter of the first 2 holes is slightly over 4" to accept the 4" dryer vent hose. (A jigsaw cuts the best, a drywall jab saw wants to get stuck. I used a utility knife. Scary!...but the cut was great.) The third hole is a half inch bigger (4 1/2" diameter) so I can use the scrap as a cover for the unused vent hole. I am using cans that just happen to be the right 4" size. The cans will be used later to stiffen up the ends of the dryer hose.
Step 2: Screened Vent Hole
Most water based lint catchers don't bother with any kind of screen, and a small amount of lint escapes. Alternative filter: pantyhose. Something that will show the lint when it has blocked the filter. But I wouldn't recommend something that can't handle humidity such as cheesecloth or a sock. 100% silicone can be used as an adhesive rather than a glue gun. Painter's caulk won't work. It's not waterproof.