help teaching Leo to poo in the yard

Hi all,
My newly adopted 5 year old coonhound seems to have some aversion to pooping in the yard. He poops very regularly on his morning and evening walks, but now that we've got the invisible fence installed, I would love to eventually be able to let him outside to do his business on his own, so this morning, at the suggestion of a dog trainer, I fed him his breakfast and we immediately went outside to poop. I walked around the yard with Leo tethered to a leash for 90 minutes! All I got was a little bit of pee - I gave him a treat and praised him for that, but no poop! Finally, after an hour and a half and about a thousand mosquito bites, I took him for a real walk down the road, and he pooped within 5 minutes - I praised him and gave him a treat and said "poopoops" over and over again while he was in the act. (poopoops and peepees are our words)

But, are there any tricks someone can share with me on how to get my dog to poop in the yard? I mean, if you guys only knew how close I was to pooping in the yard myself, to illustrate my point...

I was sorta thinking I should ONLY walk him in the yard, multiple times a day, until he poops - but not taking him on real walks leaves seems pretty harsh, and leaves him pretty bored and lethargic.

If you could stomach this method, take some of the poops from his walk and put it in the yard where you'd like him to go then take him to that location when he's due to poo, hope it works.

Oh, yes, I've done that too!

Just a thought...when he poops on his walks, does he do it on the road, in the grass, on the gravel of a shoulder, on a sidewalk...?

He typically likes to poop in the tall grass and/or on plants or small shrubs. With that in mind, I take him to the edge of our lawn, which has tall grass and weeds and plants - perfect pooping ground, one would think, but Leo's just not interested!

When we're in the house and Leo has to poop, instead of asking to go out, he wanders upstairs and poops up there! So, my strategy is to wait until I see him head up there, then grab him and hustle him outside and see if we can get a turd outta him... My hunch is that, in his previous life, Leo was caged outside 24/7 and just pooped in his kennel whenever he had to go, so he hasn't grasped the concept of asking to go out.

LaurenBev , my 2 first dogs (both adults when I adopted them) were the same. Well , one would only poop on walks and the other would only poop in the yard. They got used to poop either way after some time.