Let's face it, no one likes to get flat tires! Unfortunately it's part of riding bikes for the foreseeable future. So what's the best way to prevent them altogether?
1. Tubeless - Many people are fans of tubeless tires and for good reason. A tubeless setup typically is less prone to certain types of flats. A "pinch flat" is when your tire takes a hard hit on a rock or other obstacle, literally pinching the tube. This can create a small hole and ruin your fun temporarily. As tubeless tires don't have tubes, this type of flat is eliminated!
Tubeless setups require a sealant inside the tire so air stays where it should - inside your tire. This sealant adds as a 2nd layer of protection to small thorns and pokey things - Stan's is a popular brand and well trusted. If a thorn punctures your tire, the sealant moves into the hole and clogs it up - most of the time you'll never even know it's there.
In addition to better flat prevention, tubeless setups are more performance oriented. You get lower rolling resistance by removing the friction of the inner tube, not to mention less rotating mass. Both of these mean more speed, or more range.
So why wouldn't you go tubeless? The biggest reason is cost - for many ebikes, they don't come standard with tubeless compatible wheels or tires. (If you want to try it anyway, google "ghetto tubeless" setups.) Changing rims means lacing up spokes, etc to your existing hubs, or buying an entirely new wheelset. That's not always a practical solution.
2. Slime - In my opinion the easiest flat preventative to install - slime. Similar to Stan's sealant, this is something that seals up holes when they occur, but lives inside of your tube instead of the tire. In theory you have more flat protection as you have a tire, then tube, then slime, meaning thorns or sharp objects have to be thicker to create a puncture. No sealant is 100% flat proof however if an object creates a large enough hold. I have had good success overall with slime vs California's formidable "goatheads".
3. Tire Liners - Mr Tuffy is a brand of tire liner - a thick polyurethane rubber product that installs in between your tire and tube. It's tough and puncture resistant. These can stop many thorns that would have otherwise easily puncture straight through your tire and tube. They can be a bit tricky to install for some, but do it right and they'll last a long time! If you want ultimate flat protection, there's no reason you can't install BOTH slime and tire liners. Personally I have seen the best results with this setup - HOWEVER I've still seen flats! Sometimes there's no stopping nails, screws, or other steel objects that live on the roads.
4. Solid tires - If there's no air, there's no chance of a flat! Solid tires, or solid rubber inserts could do this, but expect to notice a substantial decrease in ride quality. There's a good reason our tires use air. I am not aware of any solid inserts for fat tires. My only experience with solid inserts is that they're extremely difficult to install, and performance is poor once done so. The jury is still out on whether or not someone can create a good tire without air, but I would not be surprised if someone accomplishes it in the future.