Have you ever wanted to keep a wall as you can see along the way /? You know what - they are reliefs of the mountains, trees, buildings, animals such as bears, dinosaurs, buffalo, etc. The only problem I see is that the concrete from sticking to the wood. If I ever get around a router I use for my relief and probably cut the plywood and screw the base shape. Then I would close the plywood with some goodcan use paint or fiberglass resin. I would use the "gel coat" type - he wax. If you're adventurous, you can build the gel coat, laundry without pre-mixed and add your own. I know guys who make this fiber (not working on boats molds). They argue that it is better - you can build a couple of coats and the final layer is added. In this way a strong protection. The thing here is if you can not wax type gel coat of paint on top - does not stick. Tothat there are no undercuts in the modules and that they are smooth as they are created.
Paint on some gelcoat mixed as directed and let it heal you should be ready to go. I think I also use a spray on non-stick as "Pam" as insurance coverage. I would try this before I go to my project, because there is a lot of pressure on the form when it is full of cement. Make sure the form is hard as you can. Use 2x4 reinforcement on the outside. If you foldyour gelcoat and then you can break concrete and stabbing, of course, have a casting in ruins. The key thing here is to prevent the concrete to stick to the form. Do everything possible to stop this and will build the wall of a great player.