You can mine copper relatively quickly as long as you know how.
1. Digging around the copper prevents enemies from getting in so they won't bother you.
2. While under the copper you are sheltered so you can place a workbench for repairs and a campfire for the Rested buff and to keep the cold away at night.
3. Mine the bottom of the ore out and let the game physics break the upper part.
4. You can process most of it on site, since most of the requirements are available in the Black Forest, so you don't have to return to the Meadows until you need Fine Wood.