I purchased two large pieces of Wedi board from Maryland Mosaics almost a year ago. I finally got brave enough today to cut out a piece. I used an Exacto knife and it wasn't too difficult. The cement coating chips a bit but I am going to seal the edges with thinset anyway so it doesn't matter. I have come up with a new way to hang the finished piece; first I want to seal the edges and install the Wedi in something else (a secret right now) and then I will take pictures and post detailed instructions (if it works). I'm excited.
Wedi is a light-weight substrate that looks like rigid styrofoam covered with mesh and then coated with a thin layer of stuff that looks like cement. I want to use it because of its light weight. I can do a large wall hanging without worrying too much about the weight. So we will see! I will post an update shortly.
I am nipping plates and bowls for the birdbath and still thinking about the design. Although I haven't posted much lately, I'm working! Today I grouted a beautiful pink stained glass and Swarovsky crystal picture frame, and then cut out the Wedi.
Here's an interesting discussion about Wedi that I participated in last spring: