Retablos are paintings of Saints. They are traditionally made from local woods, such as pine, aspen, etc. The wood panel is hand-adzed, carved, and then sanded till smooth. Then it is gessoed and painted. The painting is then sealed with a pinion sap varnish. Retablos are commonly displayed worldwide in home altars, chapels, and museums. 

Here are photos of the retablo making process: