Thin slice has many meanings. It could mean STL style (cracker), Gourmet,or NY Style. If this is talking NY Style then the best NY Pie is La Pizza on Delmar. I have had most of the NY styles in STL and everyone I know (including myself) that is from NY likes La pizza the best. Feraros may be the best for just a slice but doesn't beat La pizza for a whole Pie
Best Pizza (Thin Crust) - 2009
Laganini Pizzeria & Restaurant
4625 Gravois Ave.
St. Louis, MO 63116
The only secret to the pizza at Laganini Pizzeria & Restaurant is where to find it: The restaurant occupies a nondescript former fast-food building in the Bevo neighborhood, and the pizza is tucked away at the back of its menu, after a tempting selection of dishes from Bosnia, Germany, Greece and beyond. Keep turning those pages, friend: Laganini's pizza might not be flashy, but it is elegant in design and absolutely delicious. The crust is thin, yes, but has both body and — gasp! — flavor. The sauce betrays a touch of spice and is applied with a light hand. Toppings include the usual vegetables and meats (though the pepperoni and sausage are made from beef, as Laganini doesn't serve pork). But take a chance on one of the specialty pizzas, such as the "Tuscan Chicken Margherita," with roasted chicken, kalamata olives and fresh basil, or the "Blagica," which includes tuna fish and sweet onion. You can always order the pepperoni pie next time. After all, once you've found this place, you'll be back.