I looked at your link. This is not what I consider a beginner project. The instructions are pretty good, however, and certainly it's a very doable project.

A method that I think is easier and less complicated: Threads magazine (#120, September, 2005) had an excellent article about how to use masking tape to copy any garment without taking the garment apart. You can buy that issue, if you want, or you may be able to find the issue at a library. See the link below for a sort of preview of how this works.

If you can take the pants apart, that would be even better. Use a seam ripper to disassemble them gently (preserving the seam allowances) and use the pieces as the pattern or to make a pattern. Take note of how these have been sewn together as you take them apart. If these existing pants fit you well, you can also use the pieces as a guide to alter a purchased pants pattern. Adjusting the crotch seam always trips me up, but using a pattern you *know* fits correctly (your existing pants) as a guide would make that easier.

A book about constructing pants would probably be helpful, just to give you an idea of the order of construction. I assume that you have sewn before, just not sewn clothing? I don't know that I would choose pants as my first garment project, but that's just me! Depends on how detailed these pants are - darts? waistband? belt loops? pockets? pleats? Every detail increases the complexity just a bit.

CMC

Here is a link that might be useful: Copy garment without disassemling it.

1 thing I think is important to keep in mind about using a garment for a pattern is to copy only the garment - not the seam allowances - then add your own seam allowances - for a more accurate fit.

just my 2 cents.....

I am hard to fit and any time that I find a pair of pants that fit really good, I tear them apart and use them as a pattern. I just wear elasticized waists, so putting in a zipper and darts, etc. will be harder. Also pay attention to the type of material in the boughten pair compared to the fabric you have. That may make a difference too. If you do not have a serger and the seams are only 1/4 inch, you may want to make them larger...Hope this helps.