The core idea of this root was:
slimy, gliding, sticky
The most obvious family members are words like slime, slick, slide and slip.
The words limestone and the German der Lehm (clay, loam) and der Leim (glue) are based on the feature of limestone when its wet.
The German verb schleifen (to drag, to sharpen) is more about the idea of gliding, rubbing across a surface. The verb schleichen (to sneak, walk quietly) came from the idea of touching/grazing the ground lightly, grazing it.
Schlecht (bad) and schlicht (simple) originally referred to an even surface (where you can glide well) and from there it shifted toward bland, boring, not special and eventually bad.
The most surprising member of the family is to delete. It comes from the Latin verb linere, which meant to wipe, to smear and it literally meant “to wipe of”.