small pole barn advice

So I'm building a 24x24x10' tall pole barn with a 6&12 pitch roof. I just barely cleared an area and did the layout. I'm undecided if I should leave the ground as is and do a gravel floor, or do a concrete slab. If I do a slab, which I really do want, the elevation rises 2 feet from right to the left. So if I want to level, would it be best to remove a foot from one side and add a foot to the other? Just trying to get ideas. :) I intend to use a total of 8-8x8's for the sides, leaving the front & back open.
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This is the area I'm working with.

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Falls 1 foot over the span of 8 feet, but 2 feet total from right to left over 24 feet.

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