Yes, make the chase a minimum of 12" x 12" inside dimension for 6" class A insulated chimney pipe. But I would find out what specific brands of chimney pipe are sold there. The local brand pipe may have a different outer diameter or have different clearance requirements. We are talking about US made products. Do you know what brand chimney pipe is available locally?
Do you know what stove you will be getting?
Do you know what stove you will be getting?