Hope this helps:
The paper suggests that Lauric acid is the active agent (table 2).

It would make sense that plants would develop and produce chemicals that insects don't like. But the paper is talking specifically about blood-suckers, which aren't predators on coconuts. So that link might be tenuous.

"Aqueous-based starch composite" is academia-speak for "a slurry of sawdust and pulverized coconut". I imagine this was the media tested because it was a cheap/easy way to get the oil to stick to the cows (starches get sticky when wet).

If you want to try to replicate the results, it looks like you can for <$20. Lauric acid is cheap and safe. You can buy it online and use it as feedstock in your own formulations. But because it is fat, it will be insoluble it water unless you react it with a suitable base. Basically, you'd have to make it a soap. So it might be better to use it as an oil or in an oil solution.

https://www.carolina.com/specialty-chemicals-d-l/lauric-acid-laboratory-grade-100-g/871840.pr

Thanks for taking a look at this!

So, lauric acid. I'd latched onto the methyl ester since that was reported effective against stable flies, but that's a special case and you're right that they more often talk about lauric acid.

Do I understand correctly that Lauric acid in oil is different from coconut oil because in coconut oil the LA is in triglyceride form?

Lauric acid (according to the paper) is the majority component of the coconut oil. And: Yes, it won't be a free acid. It is bound up to the glycerin. Storing energy as triglyceride fatty acids is a common way for life to store energy.

You could probably use the lauric acid to make either the methyl ester (via methanol and a strong base, IIRC), or the triglyceride (via glycerol). I'd have to do some reading to find a suitable reaction mechanism. But either compound should be a simple synthesis.

Not certain if the methyl ester form is toxic to mammals. So that would be good to know before trying to make it. The triglyceride will be completely safe. ;-)

In the paper I've had trouble tracking when "lauric acid" means the free acid or the triglyceride (or methyl ester).

Re-reading after your 1st comment (again thanks) I thought it seemed like the authors mostly meant the free acid. Except for using the methyl ester vs. stable flies. So it seemed like the free acid was the thing.

Before that, looking up how to make the methyl ester lead to the biodiesel homebrew scene. If/when I care about stable flies, is the equation {fatty acid methyl ester} = {biodiesel} valid?

It seems like the easy way to "make" the triglyceride would be to just use coconut oil as-is. ?. But the idea for repellent effect is to liberate the free acid from the natural triglyceride rather than make triglyceride. ?.

This page might be worth a look. This is the methyl ester (it is non-toxic, by the way):
https://pubchem.ncbi.nlm.nih.gov/compound/Methyl-dodecanoate

Contrast that structure with that of the acid:
https://pubchem.ncbi.nlm.nih.gov/compound/3893#section=2D-Structure

The acid is a precursor to both the triglycerides (by combination with glycerol [I think]), and the methyl-ester (by combination with methanol). So when they are talking about the acid, they are talking about the molecule with the H-OH end. That terminal H-OH is called a carboxylic acid.
https://en.wikipedia.org/wiki/Carboxylic_acid

Take a look at the structure of glycerol....
https://en.wikipedia.org/wiki/Glycerol

Notice that it has three OH groups. It is an alcohol. Each OH group can be attacked by an carboxylic acid (like lauric acid), and will form a water molecule, and 1/3 of a TRIglyceride. The resulting bond will be the two large molecules (the laurate and the glyceride) being held together by an oxygen atom. This shape is called an ester.
https://en.wikipedia.org/wiki/Ester

>is the equation {fatty acid methyl ester} = {biodiesel} valid?
It would be closer to....
(fatty acid + methanol) ---> (methyl ester + water)

Might want to ask the biodiesel guys for specific stoichiometry, since they live it every day.  

>It seems like the easy way to "make" the triglyceride would be to just use coconut oil as-is?

Probably. IIRC, the paper said it was 70% of the mass of the coconut oil. 

No matter what you are going to try, I'd recommend you buy a quantity of the acid, unless you specifically want the triglycerides. It's thermodynamically favorable to use the acid to make anything else, but breaking the esters and reforming the acid will require a much stronger acid. Since you aren't burning it for fuel like the biodiesel guys are, you can potentially afford to buy the free acid as feedstock. ;-)

[EDIT] Point-of-clarity: The biodiesel guys are taking the triglyceride as a feedstock (because that is what Nature made), ripping off the glycerol to get back to the carboxylic acid, throwing away the glycerol, and reforming an ester to a alcohol that is more suited to their purposes (methanol). They WANT the methyl ester, and have to go through the acid as an intermediate step to get it from a natural triglyceride.