I can only try- I used to drink instant coffee in my youth, many years ago – until I found brewed coffee. I just cannot drink instnt anymore ,unless it is shabbos or yom tov. it is truly excarable, the acidity, the aftertaste- YECH ! so, when I drink, it is in only brewed coffee ! try it once- you may never go back-after all- you dub yourself ” I can only try”.
on a more sober notion- how can the element-when not used- be considered aish?? this would mean that any stove or oven is considered as lit- clearly not the case.
to squeak- “zli’ can be both- as you indicated, roasting over an open fire or “zli kli” which is actually frying in a skillet. Interestingly, I have seen coffee beans roasted in a pan over fire- this is they way ethiopians do it (maybe all africans but I only saw ethiopians do it). the skillet is heated but dry and the beans are roasted in it. They don’t burn because the beans actually have a little bit of fat in them, like all beans. Halachacally, it makes no differecne to our discussion because coffe making is clearly bishul and “jesh bishul achar afyah” and also “achar zli”