How to make cement stick to wood for verticle wall art?

I want to make an art piece as a wall hanging. Using a 4' x 6' sheet of plywood - I want to adhere cement to the plywood and then place items in the cement (ie broken bits of glass, small rocks, shells etc.) - like a collage or mosaic. Will the cement adhere to the plywood or do I need to use a special technique? This will be hanging outside on my deck so weather and temperatures could be and issue too. Ideas and advice appreciated.