Start by preparing the béchamel sauce: melt the butter, stir in the flour, and gradually add the milk while stirring constantly.
Season the béchamel sauce with a pinch of salt and nutmeg, then set aside.
Preheat the oven to 180°C (356°F).
For the assembly, lay a layer of lasagna sheets in a baking dish.
Spread a layer of béchamel sauce over the sheets.
Layer slices of ham on top of the béchamel.
Add a layer of grated cheese over the ham.
Repeat layers (lasagna sheets, béchamel, ham, cheese) for a total of 3 to 4 layers.
Finish with a final layer of béchamel and a generous amount of grated cheese on top.
Bake in the oven for 30 to 40 minutes until the top is golden and bubbling.
