My pigs had big metal runs from Bunny Business .
Metal (so no wood to rot)
Good height , about mid thigh on me . Designed to give a rabbit Binky Room so high enough for guinea pig houses inside ,
I got them a HopInn tunnel (its three tunnels that connect in the middle and they are water resistant for half an hour or so if they ever get caught in a shower)
Fold up flat for storage
I had a 84"x48" and a 48x48" (two groups of pigs) . I bought a triangular one as a quarentine run, but they're more limited space . Rectangular are better .
We didn't use a wire 'skirt' ' because guineas cannot dig , but be aware something ( fox , badger? can dig in so check round regularly . (You'll need to move it every few days anyway they are greedy 
)
We used heavy tent pegs hammered in to the earth , one each corner in the smaller run, and a couple down the sides as well in the big run.
They come with a long post that goes through metal loops but that isn't enough (IMO) to secure . (I added a few cable ties as well to the corners )
You can put a cover over . I had tarpaulin if it was windy or chance of rain. and a black fitted bedsheet for shade .
Don't leave them out long to begin with (start 30minutes then increase)
Avoid buttercups and daisies , though piggies are fairly good at this .
Make sure it s level , no gaps they can wriggle under .
Grass needs to be dry , those bellies are low slung.
Think how you're going to catch them My NDNs were treated to "Tilly stop being an arse" when we were trying to catch them.
A Gymnast DD helps .
In the height of true summer we left ours in the shady pighouse (it had secure ventilation) till after the hottest part then they grazed sometimes till 10pm if it was light . Just be aware thats when the foxes come prowling.
Then tucked up with fresh hay water light veg supper pellets and sleep.
The sight of a popcorning piggie is one to behold .
One of my favourite memories of my tiny himalayan sow was her running round in a circuit . Hiding under the tunnel then running again. And again. Bless . .