You can build the niche as suggested. The Redgard simply paints-on with a brush. I would use mesh tape on all junctures and double or triple coat with Redgard. Be absolutely sure there are no pinholes in the Redgard.
A better way is to simply buy a ready-made niche.
http://www.noblecompany.com/Portals...scriptions/Noble Niche Product Decription.pdf
A better way is to simply buy a ready-made niche.
http://www.noblecompany.com/Portals...scriptions/Noble Niche Product Decription.pdf