It would seem that once you have the ground prepared and the footings ready, there wouldn't be much savings in time or labor to use mostly pre-built vs. just framing it up and slapping a roof on it.
Here in the rainforest in the rainy PNW, sheds need to be really well vented and, even then, they slow down the drying process because the wood is stacked in a rectangle instead of a line.
I've found the translucent fiberglass roofing panels to be a quick and easy solution that lends itself to really fast drying because the wavy tops channel the water to the end of the stack which keeps the lower part of the stack from becoming wet from dripping and splashing water. Around here, Lowes caries translucent fiberglass while Home Depot only has the poly ones which are too droopy without additional support.
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I admit, the rock filled planter and wood splits used as weights look pretty ghetto, my other piles use discarded 3'-6' lengths of 2"x6" Trex decking to weight the center of the panels against wind which looks neat and clean and is easy to handle.
Benefits:
Allows single row stacking for quick drying
Sun hitting the translucent panels creates warmth and air movement to aid drying
Overhang on each side helps force breezes through the stack to accelerate drying
Fiberglass lasts longer than plywood (around here 20+ years vs. 3-4years before delamination)
Doesn't edge drip and splash bottom of pile with water/mud
Looks better than plywood or tarps
Easier to handle than plywood or tarps
I use steel t-posts at the ends. If you sledgehammer them in angled slightly outward, the channeled water will clear the bottom of the pile. These can handle a snow load but only if properly supported near each end. Most of my piles are long so they use at least two over-lapping panels (like shingles with the waves interlocking. I slide the panels closer together to reduce end overhang if expecting snow.
Lowes carries them in 26" widths (which overhangs my 16"-18" splits the perfect amount on both sides) and 8' and 12' lengths. I like the 12 footers but have a few 8 footers for added versatility. They come in two weights, I like the extra stiffness of the heavier ones for snow loads. Don't cheap out and get the flimsy polycarbonate ones! The good ones are $22 for the stiff 8' and $32 for the stiff 12'. They will last for years with minimal care. And they do help your wood dry in record time.