Square corners and tunnel-like window and door openings just don’t look right to me on natural homes. Gently curved openings and corners are much more elegant. Rounded openings have numerous advantages. Around windows, they allow more light into the home and improve the view. And they add a little extra space around doors, making it easier to pass through.
This look is easy to obtain by pinning the bottom of bags. Pull each corner of the bag to the center and pin in place with a nail. Place the bottom of the bag against the rough frame. These rounded corners can be shaped for uniformity with a board, tamper or small sledge hammer before the soil dries.