Keep in mind that some drawer slides are made to be mounted on the sides of drawers and may not work as well when they are positioned horizontally. Other slides are designed as undermount slides.
We used a pair of side mount drawer slides as undermount slides to make a quick-n-dirty pullout bottom shelf in a cabinet. The goal was to make it easier to remove and store a rarely used heavy appliance that lives there. It works, kinda' sorta', but it is not smooth and has a gravelly feel to it. For us, it is good enough.