Once you've got the embellishments in a way that makes your heart sing (!), it's time to sew the front and back together. I use blanket-stitch because I like the way it looks and how it finishes the opening.
Let me qualify this back-stitch lesson with "this is how I rigged up starting a back-stitch" because there is probably a slicker way that doesn't leave a double thickness of floss on the first stitch. If you know another way, do tell!
Start stitching at the top of the left "hump" (as you look at it). To hide the knot, start on the inside and draw the needle through the back piece, around to the front, and through both.
So send the needle backwards under the floss of the first stitch.Then come to the front and stitch from front to back.Before you pull the stitch snug, send the needle through the loop the forms. Pull until the loop lays down over the gap between the front and back. Continue in this manner around the heart until you get to the top of the other "hump".
At this point, blanket-stitch only the edge of the front piece.When you get to the other "hump", send the needle under the very first stich to create the horizontal "laying down" part of the stitch. Now continue with the blanket-stitching on the back piece.When you come to the other "hump" again, send the needle under the last stitch that joined the front and back.To secure the end, send the needle under that same stitch once more, but before pulling it snug, put the needle through the loop twice, then tug slowly. A knot will form; again, you may need to guide the knot with your fingernail to keep it from travelling up your thread away from the stitch. Now, slide the needle through a nearby edge of the felt, keeping the needle within the thickness of the felt (not sandwiched between the two pieces), poke the needle out again, and snip the floss close to the felt. This will bury the floss within the felt. Finally, tuck a token of your affection inside, and you are done! I find these wee dark chocolates at our local food co-op. I vaguely recall finding some milk chocolate pieces too. An old key would be sweet. Or those pewter tokens. A little love note...
If you have any questions, please ask in the comments, and I'll answer there, it'll serve as a reference spot. If you make some pouches, I hope you have fun. Maybe send me a picture. I'd love that!