I'm new to forestry...what is a Multi block farm? Is that like say a 12x12 or whatever area just stacked on top of each other over and over for trees or peat or whatever?
Its new for version 2.0, so its a pretty new feature for everybody. I look forward to using them.
You build a 3x3x3 structure (there's also alternative sizes like 3x4, 3x5, 4x4 and 5x5) using the new block, and it becomes a MultiBlock farm that can grow/harvest 4 different types of produce at once, one type on each side of the structure.
It's actually a little more setup than that (power, output and input blocks, fancy block area to determine where it will operate around the structure), but that's the basic idea.