Diy Door Panel Moulding . The design for my door needs chunky, deep panels. Next, you’ll use a pencil to mark where your panels will go. How to DIY a 3Paneled Interior Door // Love & Renovations from www.loveandrenovations.com Start by measuring and marking the doors to determine the size of your panels. I used my brad nailer to attach the trim to the door. Start by removing your door and thoroughly sanding and cleaning it.