When I started in 1969, we would tie a card board shaped deer to bales of hay with NO markings on the card board except a light pencil out line for the vitals, which you couldn't see at 5 yds.
Once we discovered Judo's, all the practice we did was roving and stump shooting. I never shot a 3D course or at a 3D animal. The Muzzy shoot was very similar to my backyard practice, where at times throw out 8" squares of foam at unknown distances.
No matter where I'm practicing, roving or backyard, I shoot from kneeling, uphill, downhill and upright. All and any angles always picking a spot and bearing down. Like Ron W stated, shoot at a stump, pick a spot on that stump. For me, this is the best practice to keep me sharp for the fall.