Depending on your Lasagna you need to either cook that in boiling water or one can use as is (depending on the instructions mentioned on the pack)
I still prefer to cook the Lasagna sheets in boiling water for 2-3 minutes as they become soft to cook. I once used it as is, and they were a bit dry and undone.
Once done, butter a rectangular tray around 9 * 5 inches wide
Layer a mixture of Vegetables in Tomato sauce
Add a layer of Cheese on top of this
3 cup Cheese
Layer the Lasagna sheets on top of this.
12 Lasagna sheets
Again layer a mix of Tomato sauce and cheese on this and then finish off with Lasagna sheet.
You should get roughly 3 layers of the same. Leave some half cup of cheese for the final layer.
The last top layer should be Lasagna sheets.
Add the white sauce on top of this and spread it across. the sheets.
Let it even drizzle down the dish by pushing the sheets a bit inside. (Just give them a gentle push on the sides)
Bake this in a preheated oven at 180 Deg C for 10 minutes.
Sprinkle the remaining half cup cheese on top of the last layer and bake again for 15 minutes.
Serve it hot with a slice of Garlic bread or Homemade Baked Oven chips