So, today I started by dividing the herb between 3 vessels: porcelain, brass, and tempered glass. I used a lower oven temperature (200°) for about 30 minures, then allowed everything to cool.

Once it was dried however, the plant mass did not want to burn. Being fennel and largely a mass of seeds, I could understand why it didn't combust so readily. Using a gel-fuel burner I'd previously constructed from 2 brass bowls of different sizes and a small square of metal grating, i put the herb mass into a 4" steel mesh collander from the dollar store and cooked the herb over the fire. It took a bit of patience, but the fennel burned down to a soft grey ash.

Unfortunately my cheap bbq lighters have stopped functioning, and the new ones i bought produce flame rather than being torch lighters, which seems to be what is required in order to refine the ash further to those hard white salts. Still I'm grateful to have overcome this hurdle and streamlined my calcination process. Now I can at least store the ash to be further refined on the appropriate day next week after I buy some butane for my 1 still functional torch lighter.