There's now an even better way of making block textures (although the other way still works! Just set "format" to "expanded" under "texture" of the block.

In the new way, you can make simple blocks by simply setting the "textureID" under "texture", and using the resource pack example which is available here:

https://github.com/jojodmo/CustomItems/wiki/Adding-Custom-Textures-to-Blocks

You can also now disable physics on your custom blocks (Make a new railroad block that doesn't do block physics, or gravel that doesn't fall)

All you need to do is set "physics" to "false" under "block"!