Entrances:
Every good burrow starts with an entrance! Here's two different entrance styles you can use, one for a normal door and another using trapdoors!
Normal Entrance:
One-Block Trapdoor Entrance
Planning your Burrow
Every good burrow needs a plan laid out before building begins! I personally use logs for this task (since I make use of the logs in the finished burrow itself), but you're free to use whatever blocks you wish for your own burrow building