If you ALREADY have a Simmon’s type of board, make a rocker profile from the deck and bottom using door skin ply, it will take sevearal tracings off each side before it will come into full contact nose to tail.
Now you have a profile that you can use to set up how thick you want it to be, draw this on your stock and bandsaw it out.
When this is done, line up the sticks and draw an outline on them, now you can start to spot glue the sticks together, keeping the last spots of glue about 4-6 inches from the ends of the outline, this way when you break it apart you won’t snap the ends off.
Glue 2 or 3 sticks together at a time with clamp blocks to keep from having the clamps mar the faces of the sticks, keep the glue spots about 16-20 inches apart.
When the entire blank is glued, cut the outline and clean it up, true the deck and crown it as much as you feel comfortable, clean up the bottom, adding any features you want, get everything as true as possible.
Turn the bottom rails, then the deck, tuning them with the razor or really sharp block plane to the point of being ready to start the sand out.
Now is the time to break it apart, using a block of wood to spread out the impact as you smack the crap out of it with a hammer, if you get into a trouble spot that isn’t cooperating, use thin taper wedges to drive into the seam and force it apart.
Once the blank is back to sections, plot it all out on how big you want the chambers, stagger them on each side of the planks, scribe the skin thickness and get to work, remember slow and steady wins the race, multible shallow cuts is better than an OH FUCK any day