This first thing you should notice and then immediately chuck out of your mind like you would chicken with maggots on it is the green cabbage. Both of them. Chuck them out. They have no place in hot red slaw. Keep the scallions. They do. In fact, hot red slaw starts with scallions. I slice them thinly on the bias. You don't have to bias slice them. But why not? Then, once your scallions are all sliced up (sorry, no quantities here), steep them in white vinegar along with some chili flakes for about ten minutes. Think baby pool. Think dipping a toe in. You don't want your scallions drowning in vinegar. Too much vinegar makes for too tangy slaw.
That's not the best photo so cross that out and use your imagination a bit. Now, while your scallions are steeping, slice your red cabbage as thinly as possible. Also julienne some carrots. I like to julienne my carrots with a mandolin, so that they're limp as hair. I add them to the scallions and vinegar and let them steep too, just to soften them a bit. Next comes the fun part. Wash your hands and prepare to do a bunch of tastings along the way.
The truth is, these are old photos and my thinking about hot red slaw has changed since I took these. So forget about the ketchup that seems to be glazing the veg in this shot, but remember the look of the tossed, shredded veg. Once you get your veg to this point, hit it with a little kosher salt, toss, hit it with a bit more. If you hit it with too much salt, the cabbage will exude a bunch of water while the slaw continues, pre mayo, to meld (about ten minutes). That water will result in "sauce" later on down the line. Anyway, at this point you should chuck in some dollops of mayo and some squeezes of sriracha hot sauce. Continue tasting and seasoning with salt and pepper, little more mayo, little more hot sauce, on and on down the line until your slaw suits your preference. There's really no wrong way to do it. Oh, and the reason I said wash your hands earlier is because it's easiest to toss heavy slaw with your hands. Here's a much simpler recipe:
bunch scallions, sliced on the bias
1 head of red cabbage, cored and finely shredded
2 or 3 carrots, fine julienne (you can cheat here and grate them)
sriracha hot sauce