Genesis 1:6, backed by 2 Peter 3:6 shows with all that water, a good portion was removed to form an insulating blanket around Earth. The land then, was largely smooth. Without the mountain peaks and ocean trenches we have today.

We are not told how long after that period that the Creative Days began. Nor the centuries of continental drift starting after the Flood. Allowing all the animals and people to get to settling in most all the contenients and simply walk to them. Over many decades, people have seen all of them fit together as one giant jig-saw puzzle.

To allow waters to receed after the Flood taking an entire year, major changes in earth's plates had to occur. Since most of the water came from the canopy, imagine the stress put on them! Some plates dipped to form ocean trenches. Which pushed others to push up, to form mountains.