A 9-ounce box of no-boil lasagna should have 16 sheets but I have had times where there were only 15 sheets. Don't fret! Layer as directed but just use 3 sheets on the final/top layer. Lay them side to side and they will fill in a bit as they bake.
If you want a very cheesy lasagna, use all 16 ounces of mozzarella.
Before baking, defrost completely overnight in your refrigerator. If not completely defrosted when cooking be sure to increase cooking time as needed. Do not allow lasagna to defrost on kitchen counter. Keep refrigerated for food safety purposes.
If you are baking right away (not chilling), bake the lasagna, covered, for 35 minutes. Remove the foil and continue to bake for an additional 10 minutes.
To take and bake your lasagna, keep it frozen until you are ready to depart and then place the frozen lasagna between some ice packs in a cooler.
Lasagna will keep well in freezer for 3 to 4 months.