Flush mount registers and air returns - is it OK to install them after the engineered hardwood floor was installed ?

[Ivan Turbinca]

I will have an installer install the subfloor and the engineered hardwood.
I would like to have the air registers and the air returns installed flush with the hardwood and potentially made of the same material
For that I am planning to build them myself since I have all the tools and it will be a nice woodworking project

The question that I have is more of a logistical question: is there a way to prep the existing location for these custom registers I am going to build ?
What do I have to tell the installer to do to install the engineered hardwood in such a way that would allow me later to easily install these flush mount registers ?

In this video am seeing that the guys simply cut the existing newly installed floor

 

[C.J.]

Make templates for each register by cutting pieces of wood the same size that you will be making the register covers. Tell the installer to picture frame around the templates. Whenever you’re done making the register covers you should be able to just drop them in place.

 

[Ivan Turbinca]

So the installer does not need to have the flush mount registers in order to build the picture frame, right ?
are there some standards for how wide the frame sides should be ? Will he know what he needs to do ?
Does this imply significant work compared with the case when he just need to install the floor around the existing register openings ?

 

[C.J.]

If your installer is decent he’ll be able to figure things out. How wide do you want the picture frame to be? Kinda depends on a few different factors. What do you want to look at. How about the wife. Prolly better to mock up a heat register picture frame and look at it to see what you like. The installer will appreciate you thinking about this before he shows up. As far as work, yes it is extra work so I would expect to pay extra for the picture framing.