Cut out bib shape through both layers of shirt. It works best if the picture is slightly above center.
Cut our additional layers (1-3 depending on how thin the shirt is and how absorbent you want the bib to be.) I have used the bottom part of the shirt and some cotton (that does not stretch). I used 4 layers of the U2 t-shirt, 2 layer of the brown t-shirt, and one layer of flannel on the back.
Also cut around the front next line, leaving an inch or two of the ribbing from the back of the shirt to attach the Velcro if the shirt is small or the baby big.
Sew around the outer edge of the bib. Serge around too if you can, if not trim the excess fabric so that your seam binding fits over.
Also sew around the neck line along the seem line between the shirt and it's ribbing, so that no one can see where you sewed.
Pin and sew seam binding around the edge. You may need to trim the top corners round to fit the binding nicely around them.
Sew on two pieces of Velcro, a button would work too.
And you're FINISHED just like that!