The method where you tuck the corners into each other" - that's the part that always got me too. I still have to watch a YouTube video every time I do it, but at least my linen closet doesn't look like a crime scene anymore.

Watched my buddy waste a whole afternoon chasing someone for forty bucks.

...and that twenty bucks thing would be my luck running in reverse. I once found a five dollar bill in an old coat and was so excited until I remembered that coat was my ex’s and the money probably came from a dry cleaning bag. The universe is definitely not on my side, it’s like it’s just watching me from a distance and occasionally throws me a scrap to keep me going. But hey, at least I can still get a coffee with that five bucks, so maybe it’s not all bad.

And honestly, @oscarb16's water level idea is the best bet for checking a big area before you even start digging. You just tape the clear tubing to a straight board at each corner and fill it with water, no batteries needed and it never lies about being level. I'd suggest marking the water line on each stake first before you touch a shovel, that way you know exactly how much dirt to remove or add in each spot. Really takes the guesswork out of it compared to a string that can move on you.

You're saying "numbers don't lie" but six months is just one season for most businesses... I've seen plenty of places where the first half of the year was totally different from the second half.