Trying to keep my fleece free of loose hay— and after years and years (and years) of building a new feeder every year to that end— I believe a permutation of the Premier Sheep Co design is the best, easiest, cheapest for flocks of 10+.

Premier sells the wire panels (I think no sheep need anything other than their 4″ by 4″ grid) and you supply the lumber and labor.  My only change is a solid plywood panel at the front top edge so no hay can spill down.

Build them 8 ft or 12 ft or even 16 ft (very heavy to move) long, as dividers, along a wall, stand-alone

(def) 1. Opinion from one … as to what could or should be done about a problem; 2. Information or report, especially when communicated from a distance  [American Heritage Dictionary]