For the outer pieces of the neck, the traditional Mahogany sections, I always choose to use Flatsawn wood. For the smaller inner cores you don't need to worry about Flat or 1/4 sawn. But for any piece larger then say 3/16"-ish I try to keep them as Flat sawn. I used some rift sawn Mahogany in the pics below but I wasn't very stoked on the results. I got a great neck but not a "Tone-Full" neck. Flatsawn for the outers is best and transfers tone better then the rift sawn wood does.
Pre-clean and pre-assemble your neck with your grain alternating from sheet to sheet/ laminate to laminate. By alternating grain look at the end of your board and match the pieces like this: Board 1 and Board 2 should look like this ))) (((. The smaller laminates don't matter. Obviously you can't tell grain out from grain in on a laminate of .020.
I use Paper towels, air and an unused 2" paint brush (dust Brush). I will also double check to make sure that all of my resaw marks and planer marks/ in consistencies are out of the wood. If there is a wave as a result of your planer it will show in the finished neck. Be sure that every thing is surfaced evenly and cleaned before you glue.
I use Titebond. It keeps the flex I like in my necks and It allows for just enough time to glue that by the time I clamp things are well into tack mode. I've clamped up to a 27 piece neck and haven't had any problems with separation or anything.
Be sure to over size your outer pieces. As clamping multi-laminated necks calls for lots of clamps you'll need extra room to resurface and re-square your neck before production continues after your glue up. I generally leave the outer cores 1/16"-1/8" or more depending on the wood thicker then I need them to be to cover this issue.
Here's the tools you need for a glue up. Use a roller, if you don't have one make sure your use a spreader (old credit card or equivalent) to get an even layer over your laminations. I like to teach that, "you want enough glue that makes a lightly frosted window." (What shown in the first picture is the window side of things, I added more glue.) Not a yellow layer of paint and not a clean window.
Take your pre assembled neck stack and lay it down flat. Then flip over the outer core towards you and glue that side. Like I have shown in the pictures. After you've got your first surface with glue and your ready for the next layer just flip the next layer on top of your first piece. That way your preglue grain orientation will stay the same as you work. Think opening a book and flipping the pages toward you.
Now I corner just 2 surfaces as I go. A lot of the time my pieces are not uniform or square so I use just one end and one edge to line as I glue the other end and edge don't matter as I will have to joint everything later. All my laminates get set to these two surfaces (square or not).
When I have larger glue ups with more laminates then just a basic neck (this neck is a 15 piece), I plan sections. I ALWAYS use a larger hardwood section in the middle as I want a hardwood to support my trussrod. You have to think of "end-weight" and laminate proportion as you design your neck. If every laminate is the same size there's no distinction between the colors. Who wants to just do the Hoffman/ Olson neck proportion? If your going to laminate why not make it your own. No offense any who posted, but I make sure I vary the thickness of my laminations to highlight my choices. Matching your neck laminates to your body and binding choices really can tie the whole guitar together.
Anyway, if you have more then say, 8 laminates the viscosity of the glue as your laminating will make your laminates run away from you. So with thicker pieces, in this case the outer and center core, being the caps to my 1st section I can set it aside and work the rest of the stack. And then I can apply glue to my last piece and put the 2 sections together.
I'll place one clamp at my "edge/ end corner" and tighten it to light pressure. I'll then put my second clamp on the opposite end and tighten until it's as tight as I can get it. After that I'll go back hard clamp the first clamp. Doing it this way allows for control over the laminations as you clamp down that second clamp. Other wise things just slide around as you clamp, if you soft clamp the first clamp you can hold or slide things around to keep them straight as you clamp the second.
From there I put my next clamp in the middle of my first two clamps and then I'll middle between that and the end and then middle clamp between the remaining spaces. This gives me an even spacing all the way around.
Hope this helps.
Todd