Use burlap, spray with a good heavy coat of adhesive, take dirt, twigs and leaves and throw it against the sprayed burlap. a coat of sealer over it will finish it up. You can also paint logs near the bottom to similate a fallen tree trunk. Last, attach some art fall leaves and some ghillie jute to make random color swatches. I also would recommend cutting the burlap in irregular edges rather then a flat straight edge. I also tear holes to allow light to come through in several areas.
I prefer a three stake system to form a triangle and then sit in the middle with my ghillie.