Free good lumber (suitable for the kind of rustic tray pictured in OP's post) is everywhere. It's called pallet wood. Many places here give them away free, such as my local Staples, carpet merchants, etc.
Free in cost, but not free in labor as it does take some effort to get the pallet into a proper form of lumber. At the peak, I had about 50 board feet of wood harvested for small projects.