Hello I am making a 3D picture frame which is a4 size and 32mm deep. I am putting an assortment of keys inside (dad is a locksmith) and want to fill with epoxy resin to set he keys in however I want to bring it 2mm below the picture frame level which is 32mm deep so about 30mm deep of resin. however some parts of the picture will not be that deep as the space is taken up by some of the keys. I need the surface to be clear so you can see all the keys inside and the backing of the frame which will be black. I want it to be clear but do not want to have to sand and polish it as it will be 2mm below the frame level and will be hard to sand and polish without damaging/scratching the edges of the frame. If you could tell me which resin to use and the application method that would really help me out, Thanks very much in advance!