Distress a little of the top and sides of the jar as well. (lifestorage.com)
Apply the stickers to the smooth side of the jar, and press firmly on the edges to make sure they're completely adhered to the glass. (happinessishomemade.net)
Failing to do so will increase your chances of growing mould at the sides of the jar or bowl and eventually spread the contaminating mould into the rest of your starter! (bakeforhappykids.com)