Need advice on best way to leave current office

Hi everyone, I have been at a private practice since graduating a little over a year ago. I love my coworkers and enjoy coming to work most days, but there simply is not enough work for two full time dentists. I’ve had a few good months here and there, but it’s not consistent. With no daily guarantee, it’s disheartening to have 2-3 appts spread out throughout the 8 hour day, especially after sticking it out for a year to give my patient base time to build up. I have considered asking for a daily base or requesting to reduce to part time because I really do like this office and my employer. I noticed an office in my area is hiring FT with a base pay and am thinking about pursuing it because I’ve been sitting at work for the past 4 hours doing nothing. I would love advise on the best way to handle this situation - should I talk to my employer first about my concerns (have done this in the past) or do I apply for other positions and wait to let my employer know until after I have secured a new job? Do I let my employer know I am considering looking at other positions before finding something new? I want to be respectful and end on good terms. What would you want from your associate in this position?