Here's how it's traditionally done in England: -
https://www.youtube.com/watch?v=PhzXu9pk2co
I've been intending to make one of those machines for years and never got round to it. Here, in Canada, I would make the frame out of that perforated box section tube that holds up every road sign I've ever seen, it would be perfect for the job and allow easy setting up of the required spacing of the wires. The ideal
wood here would be red cedar, longlasting, light and easy to cleave. Sawmills would indeed be good places to look for raw material, you could cleave the larger slabs and you could use anything too small for them to saw. Driftwood could be another source of supply. It's best to
staple the wires to each paling to keep everything in place.
Making fencing like this would be an excellent demonstration of a traditional craft at
local shows and you'd no doubt be able to take orders and get a lot of business while having fun chatting to the general public as well as potential customers. This fencing looks great in a garden setting and will control any livestock, if well made. You might even be able to
sell some to the show organisers for temporary fencing. Back in the days when I helped to run a traction engine rally, we used miles of the stuff to keep the public away from moving machinery and stop them getting in without paying. 3 1/2 foot or 4 foot, anything over crotch height and the job was good! We supported it on ordinary round
fence posts driven in with a post hammer on the back of a
tractor if we were lucky and a "man-killer" jug handled post rammer when we weren't. Posts were about 12' apart, more if we drove them by hand! As we were mostly farmers, for the show, we tied the fencing to the posts with red baler twine so the occasional little oik with a knife caused problems. Memories!