Draw a rectangle on your felt measuring 10" in length & 4 1/4" in width and cut it.

Using a pencil make a mark on each four corners of the felt. (From the bottom corner to the marked area = 2" ).

Fold your felt based on the drawn marks. Now you have a 2" high pocket. Do the same to the other side of the felt.

Fold the felt in half and press lightly with your fingers. It should look like this.

Before you start sewing, choose your favourite embellishment to beautify your otherwise bland looking felt.
I'm going for a funky, fun & simple theme. So I chose a fabric yo-yo & wrote 'organizing junkie' on a piece of fabric. Make sure you use a waterproof, fabric friendly pen.

Sew your embellishments in place.

Pin the folded part in place. Sew around the edges a little less than 1/4" seam allowance.

The sewn felt should look like this.

Here's the inside view of the pockets.

Fold your card holder in half again & this time press firmly with your fingers. Now you have a new funky card holder to house your cards.