Prevent falling sand/gravel (patch in an old bug)

So, I've been building a semi-randomized adventure map with some friends. One of the traps I want to add is a bunch of gravel that all falls when you step on a pressure plate hidden on top of it. While I COULD probably do this with redstone, I'm not that good with it and I want this gravel patch to be pretty big. I tried the old 2-block tall plant method, but then I discovered that it got patched out in 1.13. I did a quick search on youtube and found a new method, but the way it works prevents me from making anything more than a line of gravel. There's probably some /setblock method to get floating gravel, but I don't know how to do it. Can you please add in some way for me to get a floating gravel pile?

(If someone knows how to actually do this, please tell me in the comments.)