If you get confused, just hold it more or less upright & imagine it trying to walk on its leg stumps. Whole dressed chickens like those have their feet cut off, but the stump is where the ankle on a human would be.
It becomes real obvious real quickly which part must be the back & which must be the front/breast.
If you’re still not sure, flap their little wings & imagine which way would work better for flying. Not that chickens can really fly, but they can sure try.