Long story short, my sister-in-law made a (very tame, for the record) dick joke, and for whatever reason it reminded me of this helpful hint:
If you want to slice your sausage before cooking it, put it in the freezer. Any sausage worth its salt has enough fat that the link won’t entirely freeze, even when stored for weeks, which means you can slice evenly without much effort at all. If your freezer is a boss, or you’re in a rush, just stick them in there for 15-20 minutes and you’re good to go.
Having a very sharp knife is the only real way to slice raw sausage without everything squishing out the sides. If you’re like me, with knives that are sharp enough, this is the way to go.
PS: Slicing sausage raw adds a great texture to the meat thanks to more surface area to sear, which translates well to dishes like spaghetti since the sear can withstand the sauce. Onions and peppers cooked together with a nice spicy Italian sausage, and just a little bit of crunch to the edges, some roasted tomatoes and diced garlic thrown in – that is heaven.