above ground pole and 2x6 structure lean to

im in desperate need of quick and easy dry lumber storage area using materials I already have. there is this 24x16  wooden shed on blocks and I was thinking to put up a 12' wide x 16 or 20' long pole and 2x6 lean to on the side of it. I have a bunch of 8', 10' and 12' 4x4 poles and a whole bunch of 12' 2x6's. since I need to have easy access to the lumber I will store under this lean to like structure I dont want to have diagonal cross members maybe a couple horizontal 2x6's one a foot off the ground and another a foot from the top. all fastened with either 1/4" or 5/16" carriage or lag bolts.
im thinking a 9 or 10' pole against the building and an 8' pole about 12' out, however far from building the 12 footer will be at that angle.
poles I dont want to plant in the ground but base them on soild 4" thick concrete blocks.
I have lots of 1" thick boards to put across the 2x6's on top so I can screw down tin panels for a roof.

thoughts? suggestions? will this be sturdy enough for dry lumber storage with easy access?

As long as the structure you are building off of is solid then it should be fine. Here in the Southeastern US there are plenty of houses with porches built that way. Because of hurricanes we use strapping to tie everything together. I've built plenty of them. We would put a ledger board on the existing structure to set our rafters on. The outer corners are 4x4's and a header on top, with more supporting 4x4's in between for longer spans.

Given that the structure is solid with no racking, and the roof is properly nailed off to avoid racking, you shouldn't need much or any diagonal bracing. The only caveat being if there is no foundation under the 4x4 posts. Even if you don't want to dig and set piers, it might be a good idea to dig a bit at the surface to remove any organic matter in the soil (if needed) so it doesn't sag over time. Fill, tamp down, and level off as needed. I wouldn't try this in any place prone to strong winds, but otherwise it should work. If you are also using 2x6's as sort of 'ladder rungs' for storing lumber, then that mitigates the bottom of the posts shifting towards or away from the building. Perhaps find something to keep the bottom of the post from shifting side to side such as driving a piece of rebar in to the ground. As long as they are kept from going side to side then there isn't anywhere for it to go but up. Once loaded down with wood it would take tremendously strong wind to pull it up. It will be a fair bit of work, but when you need storage, nothing else can replace it. Good luck!

This sounds like good plan.
I would probably use 12 foot poles on the high side, and 8 foot poles on the low side.
That would give you greater pitch on the roof and a building that is roughly 11foot 4 inches across.

If possible I would anchor the highline posts to the existing building for horizontal stability.
I would also drive t-stakes right next to the posts on the low side, and connect the posts to the  stakes via lag or ubolts.

If you think it isn’t stable enough, you can put diagonal bracing on with big SPAX screws and easily remove them when you need full access.