Fill a wide, shallow bowl or casserole dish with warm water. Place a clean kitchen towel next to it on a work surface. Submerge 1 spring roll wrapper into the bowl for a few seconds until it softens. Gently transfer it to the towel, laying it flat. Dip a 2nd wrapper into the water, then lay it on top of the first one. Use a clean towel to gently pat it dry. Place a lettuce leaf on top of the wrapper, then top it with some basil and mint leaves. Arrange a small line of shredded carrots, a few slices of cucumber, and some avocado. Be careful not to over-fill. Lift the bottom edge of the spring roll wrapper and fold over the filling. Fold in the sides of the wrapper and roll to form a tight roll. Place on a platter with the seam facing down. Repeat with the remaining spring roll wrappers and vegetables to make 10 rolls.