Step 1. Wash your fucking hands! Don't go picking your ass and touching something you're gonna put in your mouth... ya damn dirtball! Now that's outta the way... I start with a Prismaster. No, I'm not trolling you and no, it's not mandatory. That said, it's only a couple bucks and easy AF to procure. I like a portioner tool for hygiene (both pathogens and dirty finger nails), and consistency of dose/load. I still hand bake the resulting tobacco brickette/nugget. Using thumb and forefinger from both hands, I compress into a rectangular cuboid shape. Careful to apply equal and opposing pressure to each side, as firmly as possible without breaking form. Rinse repeat until I arrive at something akin to a regular portion in both size and shape. The more time/effort you invest here, the less likely it will be to break apart. When it comes to shape, the ideal is whatever requires the least amount of adjustment in your lip... I like to round the edges for comfort. Also, I don't see a lot of benefit to thick chonky prillas. Operating under the assumption nicotine is absorbed via mucosa, I aim to maximize surface area. If you don't get it just right, you'll have to squish it around in your lip. Causing the prilla to fall apart and leaving you with a mouthful of shit faster. Snus is also a little abrasive and for as much as I use, I end up with irritation if I'm constantly adjusting.
I hope you like this method. Experiment with different sizes and shapes until you find out what's comfortable in your lip.