Just dig a hole and plant the flowers....don't doany tilling or digging that might disturb the roots.Maple roots are just under the soil.
Linda C

& don't add soil to the area;
one of the most common causes of stress & death to trees is planting too deeply/too much soil over the roots.

Plants, including trees, need oxygen, & covering the roots too deeply will suffocate them.

Also, be sure that the "flare" of the tree is above ground.

The tree shouldn't look like a telephone pole stuck in the ground, diamater identical at top & bottom.

It should have a slight flare, & the topmost roots should be just under the soil.

Best luck, & have fun!

I read a book once that said, "Every tree should have a petticoat". I agree, but sometimes flowering groundcovers are more successful than plants sold as flowers. Because you shouldn't add a lot of soil, you need plants with shallow root systems. I have used vinca, ajuga, lamium and sweet woodruff.