When I was preparing the foundation for my garden shed I marked the outline (after some fiddling around to get the correct lengths in a right angle) and started digging. Of course along the line first, one time around, so it keeps it shape.
Naturally I then continued working inwards and a few wheelbarrow loads later my wife commented "I thought you stopped playing minecraft two years ago?".
This picture was taken by me with cellphone camera Xiaomi Redmi note 7.
Feel free to use it, no credit necessary.