can I change my job during NIW?

My current employer already started help me with labor certificate application, but they freeze the hiring recently. So I am afraid that they are going to lay off. I want to start NIW application as a backup. Do I have to have employer sponsorship for NIW? Can I change my job anytime while I am applying for NIW? I want to file it myself instead of asking lawyer for help. Anybody gooluck at this? I have a master degree, working in a biotech company. Thanks a lot!