I guess you's need to define "slightly". You could always do a small lift block with very little effort. Not sure how small you could find one. You could even fashion one out of a small section if an overload leaf if you have the means. Not a great choice if your 4 wheeling but would give you a "slight" lift for cheap and no noticeable ride changes other than a little bit of lift.
Procedure:
truck on jack stands in rear, Loosen Ubolts, drop axle slightly, slide in blocks, raise axle to original height, re-tighten ubolts, go for a ride and hit some bumps, re-tighten u-bolts again.