Remove the pavers and lay in 4 to 6 inches of 3/4 gravel inside a frame to hold the gravel in place and to raise the base above the waters. Reset the pavers. Level. No need for a declining shed.

I hope that is your neighbor's garage window.

One other question please - How should frame it to hold all the pavers in place?

I think the first question is what kind of floor is in the shed. It it is a cheap plastic floor you need the pavers. It the floor has been reinforced such that it is on skids, instead of placing the shed directly on the ground on the paver. place a couple of blocks under the skids and do away with the paver entirely. This would allow the water to run freely under the shed, and being off of the ground, air can circulate freely under the shed,

While my shed is on wood has blocks under the skids, to cover the opening under the shed I have planted azaleas on both sides with a ramp in front.

If your base is good, the pavers won't need to be in the gravel frame. They are not going anywhere with a shed sitting on top of them.

I can't vouch for a plastic shed in a high wind staying put.