If your LSA setup does not give you negative keyword controls, the best way to reduce irrelevant searches is to tighten your services, job types, and service areas. Make sure your profile clearly reflects only the work you actually want to receive.
Keep an eye on your lead history, too. If you notice the same types of irrelevant requests coming in, remove or adjust the related services or locations where possible. You can also dispute leads that are clearly invalid and qualify for a credit.
Unlike traditional Google Search campaigns, LSA gives you less control over individual search terms, so the focus is more on getting the business profile, services, and targeting right. your goal is to reduce poor-fit leads at the account level rather than trying to block every unwanted search individually.