Fishing sandy flats differs from structure fishing in a few key ways. You can get away with lighter rigs because you won’t have to muscle a fish around/out of heavy cover. Current tends not to be as big of a deal as well. While tide and water movement factor in any saltwater situation, without structure to funnel the current, it matters less. Conversely, smaller bits of cover and more subtle bottom variations can mean a lot more than they would in more variable terrain. (I have no idea why fish hold over my normal sweet spot, but I kick straight there, have been for almost 20 years, and I always get hit there). Having a rod holder for trolling on each side of the tube is handy.
Lures are pretty standard, small grubs work great, swimbaits as well, color, action and reaction all vary. Carolina rigs work well also. I’ve generally had best luck with lures in the 2”-3” range. Colors vary like anywhere else.
The only real feature is the bottom, so you want to relate to the bottom at all times. Not necessarily touching it, but knowing where it is in relation to your presentation. With the grubs, I just drag them across the bottom. With a swimbait, I can’t usually kick fast enough for good tail movement, depending on the bait, so I’ll kick while lowering the rod tip, then lift the rod tip and bring the swimbait towards me a little faster than I’m kicking.
Most/all of what you are fishing for (barred sandbass, spotted bay bass, halibut) will be right off/on the bottom, bringing your bait higher into the water column risks more incidental catches such as pacmack and croaker.
Down on the bottom, other incidental catches (that I’ve personally seen) are leopard shark, angel shark, bat ray, midshipmen and calico.
Mentally the way to look at it is that you are fishing depth, not structure. My standard pattern is to toss my baits up onto the beach as I launch, parallel the beach at the earliest possibility, then begin zigzagging further from and closer to shore until I start getting hit.
If you are in an unfamiliar spot or conditions, be prepared for a looooong kick, and even after a loooong kick, you may not find them. Once you do, make sure to mark the spot, good luck. Should you run into structure of any sort (you’ll know when you get stuck on it) definitely work around that, especially the lee side in current or sunlight.
All that being said, your mileage may vary. My experience is centered on Santa Barbara/Goleta and Junipero. I use exclusively plastics, specifically baits I design and pour. You may have different experiences, catch different fish, use different lures and techniques. I’ve heard good things about deep diving hard baits usually reserved for LMB. Spinnerbaits are supposed to be pretty decent given the right conditions.
Don’t discount a possible spot because it doesn’t have structure, give it a shot, just treat it differently.