A slow cooker will work just fine, but I've found that making stock in the Instant Pot means that you can coax just as much flavor out of your scraps and into the stock as you would doing the stovetop method.
I am a big believer in the glory of homemade stock. Grocery bought stock works just fine for many applications, but if you want to give your meals—particularly a nice soup or sauce—that extra restaurant-level complexity of flavor, is the way to do it. You can make it from the scraps that you have leftover from making other things—just throw chicken bones and carrot tops and other trimmings into a zip-top bag in the freezer until you've collected enough to make a decent stock. ("Enough" here is subjective, but I'd say you have enough to make stock if you have the equivalent of one chicken carcass, and adding more will just deepen the flavor.)
isn't a particularly complicated process—basically you put your bits into a deep stockpot, cover in water, and let is simmer slowly for several hours. But the timing part is what is often annoying, particularly if you don't have several hours to babysit a pot on the stove. A slow cooker will work just fine, but I've found that making stock in the Instant Pot means that you can coax just as much flavor out of your scraps and into the stock as you would doing the stovetop method.
Here's the basic formula: Pile all the ingredients that you want to use in your stock into the bottom of an Instant Pot. Cover it with about four quarts of water. (This will vary depending on the size of your Instant Pot, but you want to fill it to about an inch or two from the top.) Then set the pressure to "high" for 60 minutes. Let it cook and release the pressure valve either naturally or manually. Strain and use however you want. You can play around with going a little bit longer or shorter, time-wise, but I've found an hour is about right most of the time.
It's ridiculously easy, and it has the added benefit of freeing up stove space. It's also the only way I can convince myself to make stock when it gets so warm out that turning on the oven seems like an awful plan. Do you need an Instant Pot to make stock? Of course not. But will you end up making a lot more stock using one? Maybe so! I do.