Hi Dulcamara,

I have not found any websites that specifically tell you how to make your own homemade scapulars, or what the "rules" are, but from what I have read, I know the following:

1.  The original scapular was not the scrap of wool felt we use today, but an actual garment.  It was plain brown wool and was worn over the shoulders.  It hearkens back to the days when this was a garment worn by slaves to show their status.

2.  Because of this, the only specific requirements that I have found regarding scapulars is that they must be made of 100% wool, preferably brown, on the side that touches your skin, and it must be worn over the shoulders.

3.  A good friend of mine has a collection of antique scapulars made +/- 100 years ago.  The backs are brown wool, and the fronts are beautifully embroidered or painted silk.

Using these antique scapulars as inspiration, we recently held a workshop where we taught the members of our homeschool group to make them.  

My friend made a template sheet of images that could be used on the scapular fronts, most of which were initials and symbols of Our Lord and Our Lady: The Marian initials, IHS, Crosses, the design from the Miraculous Medal, a Chalice and Host, The Sacred Heart and the Immaculate Heart, etc.  The image is there for the purpose of beautification and of giving an outward symbol of what this item represents.  As you can see by perusing the commercially available scapulars, they have widely varied images, including saints, etc.

Once the front was embroidered or painted, a cord is added and the fronts are attached to the backs with a sturdy blanket stitch.

We did all of the work by hand.  The children's scapulars were not models of artistry, but it was incredibly meaningful for them to have made them themselves.  

Many of the adults' scapulars did turn out very lovely.  Definitely not your average store-bought item!

I am trying to work with this friend of mine to put together an online tutorial showing how we did this.  I will let her know of your interest and see if we can manage to do this soon.

Best of luck!