here is my future base
I mean for many months + going on breaks, i kept my chests out in the open simply because i explore more than i build; you can be pretty secure with large-above ground buildings if you:
following those steps you're almost 99.9% sure to not get raided, getting spotted by elytra flight is almost 0 to none since elytra is primarily use at either the border, end, or on the nether roof.
Sometimes you forget that the map is actually quite massive, so as long as you follow the rules GrandpaCarl put up, you're more likely to be perfectly safe. With almost every base I know of, the only reason they were raided is because someone betrayed, accidentally tp'd someone in, or accidentally gave away coords. Rarely do 60k+ builds get found by randomly exploring.