It's three spells. Well, the first is technically optional, it's a practical matter to strengthen the glass, but if you were using a different vessel, or in this case if they don't need to be durable, you could skip it. The second is to keep the blood from clotting, and the third binds it to the mage.

I learned how, but ... The First Enchanter preferred to do it himself, at Kinloch Hold. Everyone who made Enchanter learned, just in case we were needed, but it was rare that we were. I think he preferred to keep us out of it, as much as he could.

[It was, after all, technically blood magic.]

Discreet or not, I'd want observers. Ideally at least one mage and one nonmage. And of course, anyone you and Mme de Foncé wished to be present.