Robert,
What you want to do it a pretty straight forward project. I would think well within your abilities. The best most accurate method is to scribe the line then use a power planer and/or a belt sander. However, I don't think it is really necessary unless you have some specific reason for wanting the winch plumb. Raising lines up too far off the deck can make a tripping hazard and often times hardware looks better if it's outline is in concert with the curve of the deck. Personal choice I guess. I think the pad for the winch only needs to be a little bit larger in diameter than the base of the winch. Even a 1/4" to 3/8" proud of the base is plenty. By keeping the pads smaller you don't need as thick of a pad to compensate for the curve of the deck and you fasteners will not need to be as long either.
Nonetheless, I have done this a number of times on my boat. I know I have documented this technique in several places on my web site but I could not find exactly what I was looking for (I am fully engaged at the moment) though this should give you an idea of how to do it.
http://www.farreachvoyages.com/dailylog ... rch13.html Scroll to the 22 Jan 2013 entry and there should be a few photos and a description.
http://www.farreachvoyages.com/projects ... eater.html This is the project page for the Refleks heater install. If you scroll down part way I used the same technique for the teak pad for the smoke head.
The short version is to get a small piece of wood (the same length as your prospective pad) and a small level--a torpedo level or line level is perfect. Lay it on the deck where you wan the pad to be. raise the outboard end until it's level then put some wedges under it to hold it in place. Measure the height the outboard end is above the deck. Allow for the appropriate thickness at the end board end and that will inform you as to how thick the teak needs to be.
Acquire your teak (you can laminate two thicknesses together if necessary). Next, take the teak and lay it on the deck and then use the wedges to raise it up so the top is level. Then, use a compass to scribe the curve of the deck directly on the side of the teak pad. Keep the compass plumb that is don't keep it at a right angle to the curve of the deck. Do both sides. Remove the teak, flip it over and remove the excess with a power planer, spoke shave, belt sander. Or cut kerfs and chisel the waste out then sand smooth to just short of the two scribe lines. If you are having trouble clamping the teak to the table to cut the excess you and use double sided tape. Anyway, test fit and make minor adjustments until you are satisfied.
Nothing to it. You will be surprised what a nice job you can do. If you are unsure use some scrap lumber like an old 2x8 cut off. Its good practice. You can do it in a couple of hours taking your time and stopping for breaks and philosophizing with your neighbor.
Good luck.
