Your first boss’s trust is a reference waiting to happen. Earn it on the slow shifts.

Reputation at work is built in the quiet hours, not the busy ones. When there is little to do, what you choose to do with that time is the clearest information anybody gets about you. A manager who watched you restock a shelf with nobody checking will say things about you that you could never say about yourself.

On your next slow shift, pick the job nobody assigned: wipe something, learn the till, ask what usually gets forgotten. Do it without announcing it. When you leave that job, ask whether they would be a reference.