Many use (or perhaps, used to use) hoop coops as mobile chicken tractors, owing to the light weight - so 2x6 framing was needed to keep the structure together during transport.
In my wanderings across the internet, I HAVE seen a number of fixed hoop coop/hoop run designs which are fixed in place using pieces of rebar driven into the ground. Honestly, not sure how thrilled I'd be about a bunch of short rebar stakes sticking up, and doubt the average person has (or wants to invest) in Hickey bars for bending their own steel, but you can buy rebar j hooks to use as stakes (don't need the pointed end - 3/8" par is small enough you can hammer it into almost any soil).
Typically, one end of the panel is secured using four stakes (more may be necessary, or longer, depending on your soils - sandy soils are particularly bad!) then the panel is gently bent into an arch and the other side secured. Typically, something heavy - like a few CMUs - are used to temporarily hold it in place while the stakes are secured.
I happen to have hickey bars, and sandy soils. I'd be using #3 rebar, just like those, but I'd be driving at least 2' into the ground, not a mere 12". Likely by purchasing 20' lengths of rebar, then using a cut off wheel in the circular saw to reduce them to 2 1/2' lengths before bending.
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