All you need is pure boon compound, preferably level 3, and setting resin. Get at least 10 of the first and just one resin to finish forging.
I just created a nice copper slingbow with 3 boons that way. I use less energy when shooting, projectiles are faster and the sling applies Weakness status to hit creature.
I made a video tutorial on forging ingredients and their types and what they do. It can be helpful maybe. Planning to make second part showing actual forging and possible strategies in combining different materials. Should be ready within next few days.
PS Make sure you get your Vitality up, as it decides about your forging process Stability. I had Stability 1700 for example so I could do 16 rounds of forging, meaning I could use up to 16 compounds before I had to stop as each compound uses 100-110 Stability.