How can I build a fire pit?

Do you want it more above ground or sunken down. What are you using as sides? Bricks, landscape stones...? Dig a hole the size you need to add sides, dig at least 8" lowerer that you need for gravel and sand for drainage, flatten out bottom, start building up sides.

Here's a collection of projects on the subject:

https://www.hometalk.com/search/posts?filter=Fire%20pits%20in%20Build

Here are some ideas, hope this helps: https://www.hometalk.com/diy/build/fire-pits/backyard-firepit-37736140

Backyard Firepit

Lots of folks out here use recycled washing machine drums - https://www.youtube.com/results?search_query=how+to+make+a+washing+machine+drum+into+a+fire+pit

https://www.youtube.com/watch?v=L4pDeneu1qs get yourself a piece of 1/4" hardware wire screen for the top to prevent fire danger is needed. Also rake out any dried material on ground about 6' out. I this is going to be a feature, I would put sand around it.

My friend recently made one for 50 bucks: https://www.bitterrootdiy.com/50-diy-fire-pit/