Describe the feature

This suggestion takes a different approach about #302. I suggests adding a new block (which name is described in the title) whose length, width and height are (the only things that are) configurable (to ensure its final shape is always a rectangular cuboid) by clicking/shift-clicking corresponding side with a framed hammer, similar to framed collapsible block. That way, it is ensured that each face of the block will be a rectangle, thus prevent copycat rendering from breaking.

(I'm not sure how copycat rendering deals with textures, though. I'm assuming that it can handle all possible rectangular area no bigger than 16x16 pixels.)

This is a significantly more viable option, I'll look into getting this to work