Things you'll need to "skinnify" a tie:
1) An iron and ironing board
2) fabric glue
Step 1: Split Open the Tie
Use scissors to remove the strip(s) of fabric on the back that are used to tuck the tail of tie into. Then use scissors to split open the back of the tie.
Since a single strand of thread holds the whole tie together, once you snip that strand, you should be able to pull it out without continuing to cut it, but this takes some practice. If you need to, just cut the thread as you go.
Split the tie all the way up to the skinny part.
Step 2: Trim the Felt Insert
Pull the felt insert out of the silk pocket at the wide end of the tie.
Flip the skinny end of the tie onto the felt. You'll use this as a guide for trimming the felt. (Ensure that the tie is at least wide enough to hide the tail of the tie behind itself.)
Use a marker to mark off the excess felt.
Lift the felt away from the tie and iron the tie flat.
Tuck the skinnified felt back into the silk pocket.
Step 3: Fold the Tie Over the Felt and Trim Excess Material
With the felt tucked into the silk pocket and the felt aligned squarely in the middle of the tie, carefully fold the one side of the silk over the felt. Be careful not to let the felt slide around as you are folding the silk over.
Use the iron to put a new crease into the tie as you fold. Fold and iron in portions as you move up the tie.
After you've folded one side and ironed it flat, trim any excess material.
Fold the other side of the tie over the felt. Trim excess material, but still leave enough to recreate the folded pleat (you can see this in the last photo included with this step). This extra fold of material is not absolutely necessary but it will give the finished tie a more polished look.
Step 4: Glue the Tie Back Together
Apply fabric glue to the extra fold of material you created on the one side of the tie.
Fold the material over onto the tie and press down gently to ensure good contact.
Use fabric glue to re-attach the little piece(s) of fabric that holds the tail of the tie in place. You may need to trim the width of this piece of fabric depending on how skinny you made your tie.
Let glue dry overnight.