Line a baking pan with bacon slices, overlapping them on the sides and bottom. Ensure the slices overhang the edge of the pan to fold over later. Place two lasagna sheets over the bacon at the bottom of the pan.
Brown the ground beef in a little oil. Add the diced onion, garlic, thyme, rosemary, oregano, and tomato sauce. Mix evenly and let it simmer until thickened. Remove from heat.
Melt butter in a pan, stir in flour with a whisk, and gradually add milk. Let it simmer and season with salt, pepper, and nutmeg. Keep stirring to prevent lumps.
Pour enough béchamel sauce over the lasagna sheets in the baking pan to cover them. Sprinkle a third of the mozzarella on top. Add half the bolognese sauce. Repeat the layers: lasagna sheets, béchamel sauce, mozzarella, and the rest of the bolognese sauce. Finish with a layer of lasagna sheets, béchamel sauce, and mozzarella.
Fold the overhanging bacon strips over the top layer of mozzarella, starting with the slices at both ends of the pan.
Bake the lasagna for 40 minutes at 360°F in a convection oven.
