Grammar rejection question

[Ailuri]

So, I had an article rejected for a couple of grammar issues. The first one was a misplaced hyphen, which I should have caught in my proofing, but the second one is a bit confusing to me.

The sentence I wrote was:

"it can be simple to find a method or combination of methods that works for you"
and it was rejected with the comment:
""it can be simple to find a method or combination of methods that [work] for you." -- When "nor" or "or" is used the subject closer to the verb determines the number of the verb. "

However- the actual subject close to the verb is singular ("a combination of methods") so shouldn't it be used with "works" not "work"?
"A combination" is the actual subject- methods is merely a noun included in the prepositional phrase "of methods"
Or should we base the verb form on the noun in the prepositional phrase ("of methods") if the subject has one?
This could be a CC style thing, in which case I'm fine doing it however they want me to. (Most style guides base the form of the verb on the actual subject, but maybe they are using an in-house guide.) I just would like clarification for future reference.

[Judith]

Combination merely describes the kind of "methods." Work is correct.

[Celeste Stewart]

Aye! This is one of those tough ones... (Or shall I say this are one of those tough ones?
If we simplify, we get:
It can be simple to find a method that works for you.
It can be simple to find a combination that works for you.

I believe that combination is the secondary subject, not "of methods." It's kind of like "group of students." "Group" is singular, "students" is plural. A group of students is really singular despite the number of students that make up the main group. The group is smart. The students are brilliant.
The method is simple to find. The combination of methods is also simple to find. (Not "The combination of methods are also simple to find." However, the other methods are simple to find.)

Tricky stuff. If I sound as if I'm working this out outloud, it's because I am. Hope this helps.

[Celeste Stewart]

Continuing--- I think that it comes down to how "methods" is presented.
If you wrote "It can be simple to find a method or several methods," then you'd need to use "that work for you."
But your sentence is more along the lines of "It can be simple to find a method or a combination," which would need "that works for you." In my opinion, of course.

Also, if you use commas to set off the "or combination of" section as an aside, the sentence makes sense as stated. It may change the meaning slightly though.
"It can be simple to find a method, or combination of methods, that works for you."

Fun with grammar! There are so many right and supposedly wrong ways to do it. I'm curious about the official English comp rules on this one.