Step 1: Buy Wood and Tools!
2 by 4's really came in handy. You also need: screws, washers, nails, plywood, hammers, saw- to cut wood to fit the tree/s, And other optional tools: rope, tarp, etc.
Step 2: Add a Frame All Around the Tree
This part is very important so you should use big screws and washers.
Step 3: Fill in the Frame
Should be very sturdy. You can also add in support beams to make it even more safe.
Step 4: Add the Plywood!
This is your finished flooring!
Step 5: Add On!
Ad tarp that you can support with ropes, a rope ladder, maybe even some wooden shelves! It's all up to you!