One of the best ways to make a great build is to build around the environment. Fancy plugins like World Edit and Voxel Sniper aren't always necessary. In the real world, people can't just edit the environment to their every whim and need. They have to work around it. Not only does building around your environment help to make your build look nicer, it helps to make it look more realistic. In the above picture, I could only make a small house because I wanted this build to work with the environment.
Overall, using the environment to your advantage makes a build look more realistic and helps it to look even more amazing.