I haven’t crafted one yet, but I think I have seen several in the world already. As far as I have seen, a cog is needed in order to build those. Nevertheless the spark generator kind of looks like an altar.
My suggestion towards building and crafting machines would be to make their crafting ingredients visible. So the cog could be spinning and turning at the spark generator, showing the machine is active. And making it easier to remember basic crafting ingredients.
I hope I haven’t mixed up the items here, but if I’m right with my assumption it would be great if the devs could adapt this idea, although I believe they already have plans for it.