I bought 2 sheets each of black, white, and red felt. I used red glitter felt - but it's hard to capture that in the picture. I found cookie cutters and traced them onto cardboard to get templates of the circle and heart shapes. And then I used spray adhesive to put the hearts on the circles. But beware - that spray adhesive is a beast to get off your hands. I tried using nail polish remover and that didn't help much; I guess I shellacked my fingers pretty good.
I hand stitched some black embroidery floss around the white circles to add a little to those ones since there wasn't the glitter detail there. Since it's hanging in a walkway, I also cut out hearts for the back side as well, so there are hearts on both sides of the circles.