I had this Linden tree 'professionally' planted by a local nursery 6 years ago and it's about 4-6" too deep! I just uncovered the root flare and cut the suckers. I need to trim up the suckers better, but not sure exactly how to go about it. Use a knife and cut them off close to the trunk? Or just how ever much the pruners get? Do I need to use tree wound goop? The tree is sunk in a bit and rain & snow melt will pool around the trunk so I know I've got alot of dirt moving to do. No fun! Lawn on the north side is too high The tree looks pretty good and really took off the last couple years. Thank you for any replies.

Use pruners and no tree goop. Wounds heal faster and have less chance of disease issues if they are left uncovered.

I stepped on the suckers a little which moved them enough away from the tree to get the pruners in close enough for a good cut. I think I might have the hang of this now. And moved a little more dirt in over the roots, but not covering the root flare or where I cut the suckers. Supposed to get some rain in a few days, so I'll soon see how much more dirt scraping I need to do so it doesn't pool water at the base.

Usually, cutting suckers encourages them to branch and become an even bigger problem. Its best to pull them off when they're tiny and pullable - unfortunately those suckers are beyond that.

I use a product called 'Sucker Punch' to control suckers on my fruit trees. You will have to do some research to determine if this is a good choice in your situation.

Wow. Yes, it was planted too deep and soil covered the sucker growth.
I didn't know such a product existed. Thank you so much. Will check it out.