I use a Coleman cooler to keep things warm, similar to Cambro food storage. An advantage is since there isn't additional heat things won't dry out. I've had success holding a turkey, brisket, casseroles, etc. for an hour. I put a heavy towel on the bottom, the foil-covered item next, and then another towel over the top. The lasagna sounds like a candidate for this. I'd time it to be finished when the other preparations need to be started so it's one less thing to worry about and you free up your oven for warming.