Hello. I would greatly appreciate advice for making moulds for picture frames. As you see in the photo attached to this post, I have a master that is made of acrylic. There are four parallel sides and a top lip that is perpendicular to the sides. I was thinking about casting it so that the top of the lip is exposed. this way i only need a one part mould. Gravity will level whatever material is poured into the mould to create a flat surface. But perhaps there are problems with this method that I am not aware of?