When it comes to the development of a formulaic spell, how can a player describe their research? Is it as simple as a magus trying new words and hand gestures until the desired effect occurs?
Furthermore, what role does the laboratory play in this process when it comes to in universe reasoning. Is access to lab tools and strange ingredients needed to develop a spell that consists of only words and gestures?
Words and gestures are just an aid to cast a spell. They are not what a spell consists of, and are typically not even necessary.
When researching a spell you need to figure out just what magical forces need to be used, and just how they are to be used. Plus of course practicing the mental contortions needed to let loose the magic.
When casting spontaneous spells you do much the same "on the fly", but since you don't have the time to do precise calculations and measurements, and instead have to rely a lot more on experience, intuition, and rules of thumb, you won't be able to cast nearly as powerful spells.
The above is one way of viewing things, and should do well.
However, we do not have an official description on exactly how a magus invents a spell, or the details on how a spell is cast. Some we may infer from the rules on how spells work, but a lot we get to make up to fit our own vision.
One can infer some of the actions that goes into researching spells by the content of the lab, which is given in Covenants.
That includes:
All of those point to the study of the world around the magus, trying to determine the things that influence the flow of specific magic around him. So studying the ingluence of heavenly bodies, of various substances and conditions, the afinities of various substances and mixtures to the magic desired, etc.
More specifically for inventing a formulaic spell, one can expect that the magus will cast various spontaneous spells in order to determine the right manipulation of energy, so having some sort of appropriate setting to control the magical energies. So a pentacle drawn on the floor, candles or some ways to draw mystical symbols to focus energies, appropriate things to cast such spells at, etc.
Hope this helps.
If you have a workshop to experiment through potions and other charged items, it might look like that. If you specialize your lab to experiment through spells, you get different requirements.
For experimenting spells, there are 2 ways to be safe: retreat to an antechamber, or cast outside from a balcony. Check Covenant p120 for more ideas.
I greatly appreciate all of these answers. My normal group is usually quite questioning of what every scene looks like so I like to be prepared.
One of them is thinking about creating a House Verditius Magus that is focused on carpentry, and he thinks that his magus will have flashes of insight about how to create a formulaic spell while woodworking in his lab. Is this plausible enough?
I don't see why not, at least in part, there's no reason for every wizard to approach magic in the same way
Considering that it is possible to have a Mental Laboratory to invent spells, I would tend to believe that inventing/learning spell is before all a mental exercise. All the props are present to help the mage, but not entirely mandatory if the mage is skilled enough.
So the three months (or more) to learn a spell includes as much as figuring out how to harness and control the magical flow to produce the effect, but also how to do that quickly - within a handful of second. So there is probably a fair bit of the invention part that is about repeating and repeating until perfection, like a martial artist would do his kata.
One can speculate if the spell invention requires opening some channels inside the mage's mind and body to canalize the energy.