Base / Fixings for large gazebo

[timetex]

We're planning to put a largeish (5.9m x 3.4m) rectangular gazebo in the garden of our holiday cottage. Next to the gazebo, I also want to put a smallish shed (looked at gazebos with 'summerhouses' included but the shed is for storage not for lounging in).

Basically this: https://www.tuin.co.uk/Superior-Gazebo-3.4x5.9m.ht...

With a shed next to it.

Also going to clad one long end and the short end nearest the shed with wood to match our new rear porch, and maybe up to 1/2 height on the other short side.

I want a decent 'floor' inside - probably a slabbed base, extending under the shed, and also extending outwards on the openside to create a walk-way and even an area to pull the table / chairs out.

Question is - would you put the gazebo up using something like metal post spikes set in postcrete and then do the slab work around it OR would you put the slabs in first and then try and put the gazebo over it?

Or something else?!