From Betty
 
 The collars made from Battenburg lace are very easy to make - but rather
expensive.  The centers of the doilies are cloth so you simply lay your collar
pattern down and cut the neck opening to fit and split it down the back.  The
6" doilies fit the dolls. You can bind the neck with bias tape to make a
detachable collar or sew it into the neck as you would any collar.  They come
in round and square shapes and are sold in many places, including Home Sew
catalog, Walmart, and every craft store I've ever been in. The Wimpoles of
Barett St. (or Baretts of Wimpole St. - I forget which) specialize in imported
Battenburg lace so they have many ideas on how to use the doilies.  Just be
sure the center fabric is large enough to accommodate the neck opening and
you're in business.
  I love making these collars.  They are so simple and so regal looking when
finished.  

Also from Betty

I do detachable collars several different ways - sometimes with a row of lace
around the neck, other times with a bias tape binding, which is faster. For the 
fastening, I extend the neckline bias tape about 1/2" (if I'm using it) and 
put the bottom half of the snap on the extension so the two back edges just 
bump and don't overlap.
If it is going to overlap you need to add seam allowances. One trick I use is 
to trace several collars on white fabric so they are almost touching.  I have 
round, square, and long V templates. It is much easier to use hoops when 
embroidering on this larger piece than it is on individual cutout collars.  
After the embroidery is finished I cut them out and sew lace around the 
outside edges stopping 1/4" from back edges. Then I pin the collar, face down 
to a plain piece of white and stitch all around the outside edge and up the 
back before I cut it out. After trimming and turning I finish the neckline 
and fastener - either a snap or velcro. If you use the tape binding trim off 
1/4" of collar opening so it won't be too tight.  I've found that working 
with the larger pieces is so much easier. Right now I'm working on a set of 
eight.  Sometimes I only do four at a time.

From Virginia

I don't do snaps on detachable collars, because it requires an overlap.  
Rather, I use a hook and eye, the eye being the loop style.  I place both on 
the underside of the collar, placed so that the backs just meet but do not 
overlap.  Alternatively, for crocheted detachable collars, I crochet on a 
loop when I am edging around the collar and fasten with a mother-of-pearl or 
pearl button--sometimes a crystal button if it goes better with the color.

I prefer to line the collar rather than doing a bias binding at the neckline. 
 Then, right sides together, I sew most of the way around, leaving a small 
opening in the back; clip seam allowances; turn, press, and blindstitch the 
little open spot together.

    Source: geocities.com/heartland/cottage/5685

               ( geocities.com/heartland/cottage)                   ( geocities.com/heartland)