Now that you mention it, there is no way to specify a recipe to get the inverted one. It's because it is the same block, but the items have different metadata, resulting in different state when place.
When you set a recipe in the JSON, it crafts the ItemStack with default (0) metadata. I need to add way to allow metadata for the crafted item.
As for the textures, there is currently no special way to specify the "sloped" part directly. However you could cheat a little :
The code says to get the bottom, top, front or sides when necessary, and in case they're not specified, to fall back to textureName value. That means if you have textures block, AND textureName, you should be able to have a different texture for the "sloped" part. (Though I haven't tested that.)
From the log :
[17:01:04] [Client thread/ERROR] [ddb/ddb]: Failed to read example.json : com.google.gson.stream.MalformedJsonException: Expected name at line 53 column 3
I messed up the JSON, an extra comma that shouldn't be there. I'll update the link later, but meanwhile, you can edit the JSON yourself.