Where did you get your slate?

Local rockscape shops.
I have like 2 or 3 around me haha.

Check for any rock selling places in your phone book or internet.
 
do you have a landscaping place near you? i have one near me that basically gives away its broken unusable pieces.
 
I found out it is not always that easy to find. I went to an LFS that sells it and was told by the snotty little guy at the counter that they only sell it by the pallett and not by the individual piece, that is until I talked to the owner. Look around as Red Wall suggested for places that sell rock to construction businesses in your area. Also I know it may sound weird but calling places that sell tombstones also may work. Good luck in your hunt.
 
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