Ingredients or techniques to a more solid lasagna What are the crucial ingredients or cooking techniques to a more solid, or "brick" like lasagna? Most lasagna I've seen tends to get a bit sloppy in the pan as it's being dished out but I have seen lasagna that comes out very firm and solid. Is this due to a certain combination of ingredients, a cooking technique, or both?

For example, I've seen recipes that use cream cheese and eggs instead of ricotta, and various combinations of tomato paste, sauce, and crushed tomatoes. I've also seen various (relatively close - usually 350-375 for 45 minutes to an hour) cooking times.
I have the same preference. Three things that work for me:

(1) If you are using any vegetables, saute them to get as much liquid out as possible in advance. For spinach or other greens, actually squeeze the water out using a tea towel or potato ricer.

(2) Use less sauce or make the sauce thicker. You can accomplish the latter by starting with thicker ingredients (tomato puree vs. chopped tomatoes), or by reducing it on the stovetop somewhat first.

(3) For ricotta fillings, indeed add a couple of eggs to help them setup. 

Here is my spinach and ricotta lasagna recipe, which as you can see from the picture, sets up very firm and sliceable. And I've also got a summer squash and portabello mushroom lasagna which illustrates points 1 and 2.