Distances from the stove to flammable walls is determined by the manufacturer of the stove and your local building code.
What constitutes a flammable wall and how you can reduce the distance of a stove to a flammable wall is also determined by your local building code.
So what techniques you can use to shorten the distance between a stove and a wall surface needs to be determined professionally by the manufacturer and your building code enforcement office.
Once an approved plan has been derived at by the code official, you can find approved wall treatment products at local fireplace and stove supply retailers.
Do NOT attempt to determine what products to use or how to reduce the clearance yourself.