I was just wondering if drawer slides will function properly in the long term if oriented in a flat position? I'm using them for a keyboard tray, so nothing heavy like a drawer.

EDIT: My reason is that the original keyboard tray was attached via custom sliders which wore out. I wanted to replace them and bought several sliders from amazon, but they are a too thick by a few mm so the tray (metal) will not fit between them. I could not find thinner than 0.5" sliders on amazon so my alternate solution would be to affix them to the sides using an L-bracket and orient them flat instead so I can screw the tray on the top of the slider instead.

Alternatively I might just ditch the original tray and cut a custom piece of wood that fits more precisely, and forget about the flat orientation of the slides.

For reference my original sliders - https://www.reddit.com/r/cabinetry/comments/1h4z5qs/unable_to_access_screw_to_remove_drawer_slider/