Slate is a natural product which has its own unique shape and contour.  That is why every piece varies a bit in size and shape, no two are exactly alike.  Some slate has more minerals, some less on the surface of the slate, since minerals are a natural part of the slate. Slate needs no special preparation for painting. Just wash the surface with water to remove any possible stone (mineral) dust and let dry. When dry, use a large (usually 3/4") flat brush to basecoat the slate (including the rough edges) with acrylic paint (usually white) and let dry.

Some designs have a drilled, unseen steel wire on back for easy hanging.