On my first experiments with using LED strip lights to illuminate stained glass panels.......the logic went like this........

-Apply strip lights to back panel of wood box so they were pointed at stained glass panel

-Add diffusion method to hide LED hot spots

-Purchased first LED strip light, found you can make 90 degree turns without cutting the strip and either soldering
 or using special connectors. Dropped idea of putting strip on back panel.

-Make wood box bigger than stained glass panel and make 3 wraps of strip light around the inside of the 

  box, which is bigger than the stained glass panel, and you don't see bright spots from LED emitters.

You can see this experiment on this web page.

I developed a standard design for the wood box and used it on about 6 of my stained glass panels.  On some panels, I had clear glass in the center area and it was possible to view through the clear glass and see the LED bright spots.  To counter this, I developed a "wood dam" concept to hide the bright spots on panels with clear glass in the center.  I also added additional angled wood deflectors to try to get more light in the center of the pane.

I still wasn't happy with getting enough light to the center of the panel, so I decided to revisit putting the LED strips on the back panel, then using a diffusion material.

I Googled and looked at youtube videos and found where people were cutting the LED strips and then soldering them.  On the LED strip I buy, there are 2 solder blobs on the light strips about every 19 inches.  This is too long for a standard stained glass panel.   I tried soldering at the blobs, and that worked ok.

The strip also has copper "Lugs" about every 2 inches, which is ok for standard stained glass panels less than 16 by 16 inches.  I was able to solder wires to these lugs, but it is tough to avoid the solder running together, which would make an electrical short.

If the solder blobs were every 2 inches, this would work fine.  To make a serpentine shape, you cut the LED strip at the solder blobs, then solder a short piece of 22 gauge wire which will bend around each curve at the ends.

I ordered a selection of LED connectors from Amazon.  They are designed to attach at the copper lugs. I tried one and it worked ok on my LED strip.

I updated the box design to have the LED strip mounted on the back panel, and to use a diffuser material as well.

On my 1st experiment, I bought a 2x4 foot frosted panel from Ace hardware designed for 2x4 drop-in fluorescent light fixtures, and it did not hide the bright spots.

Further research suggested wax paper, and I also discovered parchment paper by Reynolds.  In my new design, I can sandwich either wax or parchment paper between 2 sheets of the ACE plastic panel.  I can quickly try many different materials as diffusers with my design.

Note:  Using my standard box design, there is only about 2.5 inches from the LED emitters to the stained glass panel.

            From a diffuser material selection, the more the distance, the less diffusion you need.  Having only 2.5 inches

            is a challenge with respect to material selection.

I decided to use one of my simple flower panels as a test panel.  It is 8-1/8 by 10-1/8" outside dimension with the border being 1/4" wide.