I'm at Home Depot, they only have pieces like 1x4, 1x2, etc. but they have fjp.
The minimalist design does not include traditional posts. It's smaller pieces like the fjp you are finding, joined together in an "L" shape to make a "post". Sounds like you found the right stuff. Here's a link showing what I used (in various sizes).
Thanks Big, I have the triple plush from syfabric. I feel like I can see the white of the post when I hold up the velvet, but I'm also right up on the posts. I'd imagine light spill past the actual screen frame wouldn't be an issue for the wall frame.