One of the unsung heroes on Boston's Sicilian scene is the square slice from Leone's in Somerville. Unless you are willing to splurge for a half ($13) or whole ($26) sheet tray, then lunch is the time to hit the Winter Hill pizzeria. While Leone's offers some slices in the evening, you can't necessarily count on their availability and the variety is much more limited. The lunchtime counter is known to accommodate a half dozen or so varieties at a time. More