Blends in really well!

Step 1: What You Need

Wood
Leaves
Ladders (optional)

Step 2: The Base

This is mainly a picture guide so yeah. But this is what you do!

Build a stack of wood.
Make a leaf floor.
Put ladders on

Step 3: The Walls and Roof

So build walls. Then build a roof. Easy!

Step 4: The Dome.

So this bit is hard. It is actually easy but hard to explain. Look at the trees around you. See how they have a sort of dome on them? Build that. So make a platform on your roof but make it smaller then the roof already is. Keep doing that. Then it looks like a tree!