
The walls were rather easy. Just 7 blocks high, so add 6 blocks to your base.
Basically:
Step 1: Add 6 blocks to your base.
Step 2: Complete the circle to equal heights.
Step 3: Complete!
Super simple. Takes a while to do it manually but there is a cheat code //wand. So you create one vertical column to your preferred height.
So say you were working on the row of 14. You start on the left and add blocks until your preferred height. You left click the top block. You would then go to the right hand side of the 14 blocks and tap the last block in the base row. Then type the cheat //set red or whatever colour of block you want. It will fill in the blocks from the left to right side to your preferred height. I'm pretty terrible at this sort of stuff so I placed blocks manually. But I do suggest you try the cheat codes at least once just to try them out.