Sorry for offtopic dear mods but this is too interesting, maybe we should split this thread 😉
Water always finds its level just *because* of gravity. I don’t fully understand the question or problem. Obviously whatever floor you have installed in your life will not be big enough to be impacted visually or functionally by the curvature of the earth... but sure, if you were to lay 50 miles of tiles and each individual one of them is level, if you were able to “zoom out” you would see that it’s in fact curved. Every tile can be perfectly level, but it’s only level perpendicular to the earth’s center of gravity. The first and last tile you lay will not be positioned the same way compared to each other. A bacteria walking around on a balloon is also not aware that it’s on a spherical object.
Regarding the beaches, next time you go to the beach, bring your binoculars. On clear days, look at the ships in the distance. Notice that the ones further away from you are obscured more at the bottom and look like they are half under water; curvature. The other way around also works; sail away on a boat and keep looking at the beach. If there are mountains/hills near the beach, there will be a point where you won’t see the beach anymore, just water and the mountains right on the horizon. Given clear skies and good atmospheric visibility, there’s a point where you will see just the peak of the mountain over the horizon. Again: curvature.
Nobody will be able to show you water sticking to a spinning ball. On earth, anyway, since you will have to compete with the earth’s gravitational field. If you were up in space and have a ball with adequate mass, water should “stick” to it, though it’s actually just attracted to it, but that’s semantics. Of course, if you were up in space, you could just as well turn around and look at earth being all round anyway
All of the science and experiments proving this really is repeatable and testable, but I think the problem is more that flat earthers don’t WANT to see it (and to this day I don’t understand why). Science isn’t a dogmatic belief, and there surely are wrong theories in various scientific fields that will be retracted, corrected or adjusted in the future, critical thinking and further research will ensure that. But the earth being round is not one of them. The scientific community has moved past that uncertainty, and you should too.
Tl;dr a flat earth is absolute nonsense, sorry