What's the best way to turn a galvanized trough into a shower basin?

Hi Claire! Here's a Youtube video that shows how someone else used a galvanized tub as a bathtub basin. https://youtu.be/2DTNiwGnolQ At the beginning of the video they show how the cut the hole and installed the drain.

Here's how someone else did it: https://www.danslelakehouse.com/2019/03/diy-stock-tank-shower.html

You may want to somehow seal or line the tub. We used an old trough as a fish tank and the galvanized metal leached into the water. Needless to say, we lost all the fish. ;

It will look real good for about six months but it will rust galvanized doesn't hold up like it did back when I was a kid. I did this it rusted I was very disappointed. I had to change it at one year it was a disaster by then. At six months it started rusting. Good luck. I even sealed it when I installed it.