Lurksmore has right idea but seeing them sunk in fairly far, usually in draugr villages just means you will have problems replicating it for missing pieces. So in that case you run piece over from another side and then attach from bottom. You may have to sit your character down to see the bottom of beam. Convoluted but possible. When building you really only want all base pieces to be blue then work up, or may have to fill in with a bit of dirt. Sinking stuff in doesn't make it stronger. Luckily with draugr structures they don't go up high enough to make a floaty bit or two a problem. You can also start using reinforced metal beams to cheat a bit and sink them within regular beams. Many ways to skin the cat.