I have an old maple tree which has several rather large roots above ground. This tree is also mounding up and is now approximately 10 inches above ground level. I was hoping to build a short planter around the tree to give the illusion that the ground was level. To complicate things, my yard is at a slight slope so I would have to level the ground in order to make this planter. Would I damage the tree by cutting off the roots sticking out of the ground or by cutting into them to level the ground?

A tree can stand to lose some of its roots. To lessen the shock, you might do part this year, and then wait until next year to finish. Cutting the whole root off and removing it will be difficult and do more damage. I often use a sharpened pick ax, and only cut the root down level with the ground.

Removing some of the top growth will help with the loss of roots. If any of it is crowding the house, that would be a good place to start, or low hanging limbs making it hard to walk under. Avoid the flat cuts like conventional tree topping. They lead to unsound sucker growth in addition to being ugly. Instead make slanting cuts just before a major branch. New growth will go into the branch, not suckers.