Welcome, Best place to start is with pictures of where your thinking of building and what type of soils do you expect.?
Many here happy to lend a had and advice from our own experience. I put together a blog of my build with lessons learned and things to think about in building a pond and Bog. hope IT HELPS IT IS LARGE sift through the pretty pictures there's lots of helpful info through out https://www.gardenpondforum.com/sho...r-2023-12-000-gallon-koi-pond-full-build.141/