How to make hay somewhat depends on your local climate. Here I let it dry for 2-3 days. I cut it with a scythe, spread it, turn it over once or twice a day, rake it to lines in the evening so dew doesn't make it wet again, and start all over the next day, sans cutting. Dry, sunny days with at least a breeze blowing are best. Even when it feels brittle dry the first day, it needs at least another, I think there's water in the cells that takes some time to get out. If the air is dry and warm imho it is even better to put it in the shade after a few hours and let it dry out there.
Once dried and stored, check the next day if it still feels dry in the center of the pile the next days, if not or if it gets warm there keep drying it.
It's some try and error necessery, depending on what you mow, local climate and resources.
I either store it in an airy shed (mine isn't optimal for that) or press it to bales when completly dry with a simple DIY manual press, the bales are stored under the sheds roof, off the floor and away from walls to avoid condensation.
Smaller batches, like nettles, apple leaves, and other treats, get just loosly stuffed into open cardboard boxes after drying.