First you need to make Bolognese Sauce. You can make it even the day before or the month before and freeze it. When you need it, defrost in the refrigerator.
The second preparation is Béchamel. You can even make it the day before and store it in the refrigerator, covered with cling film, put in contact with the sauce..
Now you need to make lasagna noodles. If you prefer to buy them, get some lasagna ready for the oven.
Now that you have all the main preparations, start assembling the layers of your lasagna bolognese.