As Rob and I get our heads around the fact that we are now proud owners of more than 20 square feet of slate intended for our countertops , we've started formulating a plan.
I did some research about slate (after the fact, of course – our purchase was something of an impulsive decision) and discovered it's actually a great choice for countertops . Turns out, it absorbs less than granite and you can buff out scratches with a sponge or steel wool.
We'll use mostly leftover supplies from our shower boondoggle  (it still feels too soon, but maybe someday I'll be able to blog about it), including cement board and appropriate screws. We may adhere the slate with the leftover polymer-modified mortar we used in the shower, or we may use a specific adhesive  – we're still researching  what will be best.
We again borrowed a tile saw from gracious friends, and Rob suggested creating templates for our slate cuts with sheets of foam core. He's a smart one, my husband.
After we get the slate in (I'm thinking rather than try to cut out the sink hole from the sheet, we'll actually cut four separate sides), we'll use clear silicone to seal the seams and around the sink. Next comes a round of stone sealer and we plan to maintain it with a layer of mineral oil as needed.
Now, will this project go as smoothly as I'm expecting? Probably not. They never do. (My backup plan before starting a large DIY project: have enough money set aside to hire a professional in case the whole thing implodes. This is no exception.)
But we love the slate. We laid the sheets out in the yard Monday and carefully scrubbed them down with soap and water. We first scrubbed and scraped the smooth sides and then turned them over, revealing a more natural, rippling surface. The chalky residue of the adhesive that kept it on the classroom wall scrubbed right off, although we had a little more trouble with the yellow lettering that said “top” and “left,” among other indecipherable scribbles. We scrubbed and scrubbed before we got most of it off.
Because the backside cleaned up so well, I think we've decided to use it as the outside surface. I cannot wait.
This Flickr photo  gives you an idea of the texture we found on the back of our slate blackboards.