Today's lasagna can be eaten warm. Is a mussel lasagna with tomato which is prepared in a moment and which also includes canned corn.
As always, the lasagna sheets they have to be cooked previously as long as the manufacturer indicates it. If you prefer to use the lasagna sheets that do not require prior cooking, you will have to make a slightly lighter béchamel (less thick) so that the pasta is well hydrated.
I leave the link to another lasagna where you can read and see how I have prepared the béchamel.
More information - Pork sausage lasagna