In the inventory, the metadata is still 0 as you set it to another value, in the onBlockPlacedBy method, and you check if the side is the bottom or the top of the oven, and then set the texture. Else, you check if the metadata is equal to the side, so a metadata is 0, and the bottom face is 0, so it sets the front texture to the bottom. If you want to face the oven the same way as all the vanilla furnace, check if the metadata is 0 and the side is 2, and then return the fron texture. But you need to do it before everything else in that method.