A sandal is an open top footwear with a solid sole designed for outdoor use. Sandals primarily attach the sole to the foot via a vamp (solid or adjustable) over the instep. They often also have an ankle strap attached to the vamp and to the heel of the sole.
Some regions distinguish these from a variant comprised of a thin nonadjustable vamp over the base of the toes connected to a post that slips in between the toes as jandals, thongs or flip-flops. These never have an ankle strap.
Sandals and spanking
Sandals are popular for spanking in many countries, probably because they are within quick reach. According to Urban Dictionary, "la chancla" is a Spanish word for a flipflop when used by a mother to spank her child's butt. A spanking meme shows a flip-flop sandal with the text "what it is" and the same sandal edited to look like an automatic fireweapon, with the text "what what it looks like in mom's hands".