Carpenter's Blocks is a mod created by Mineshopper which adds Customisable blocks to Minecraft in Attack of the B-Team.
This mod adds slopes and a custom variety of vanilla-inspired blocks to the game! They may look like ordinary frames or wooden blocks in their base form, but they can actually be covered with nearly any block in the game. The frame will inherit the cover block's texture and most of it's other properties including flammability, explosion resistance, and more.
In addition to covering the block with almost anything, you can also overlay any of the blocks with grass, snow, hay, web, mycelium or vine.