For hard and clay soil:
You can add some Gypsum to clay soil to loosen it up, don't walk or step in the soil, and toss in some compost next fall...tea bags, coffee grounds, shredded leaves, fresh cut grass, banana peels. Mix, cut up big chunks, and bury them in a channel you dig into your area. I dig about 6".
No fat, no animal feces or litter, no meats. You'll get yourself some animals digging that up, and creatures and insects of a type you don't want.
They used to say add sand but now they discover you have to add the perfect amount, or you actually harden the soil. It's also now recommended we don't till, or upheave the soil....compost, I think, is your best helper.
I had rock hard, eroded, "dead" clay on a slope when I moved to my new place! Ugh.
It had been herbicided to death, walked on, there was no life whatsoever on it or in it.
A year later it has worms and the occasional butterfly or bee, it's easy to work in, it's nice darker brown. So I know compost works even in the toughest spot of hard or clay. Cuz that's all I did, is add compost, and the occasional bag of manure soil.
Your Compost Master....