Cue your trusty circle punch. Size dependent on the project at hand - for this quick demonstration, I have used a 3/4 inch circle, and an oval of card, cut using a Coluzzle template.
All you need to do is punch out lots of circles, and then apply repositional (non-permanent!) adhesive to the back of your oval (or whatever it is you are 'scalloping'). You only need to put the adhesive around the outside edge of the shape - just enough to hold those circles in place. And then you get to work positioning the circles. This is where the repositional adhesive proves a winner. You can rearrange as much as you like until you are happy with the spacing. (As you can see some of the circles aren't perfect circles, and that is okay because that bit will be hidden anyway!)
The final step is to use a more permanent adhesive. You don't want all that carefully positioning to fall off on the floor! If you want you can do each circle, one at a time, sticking them to the oval, but I am not that patient. Instead, I applied the permanent adhesive to the back of the oval and all the circles, and stuck them on the front of the card. I figured that even though the circles and ovals are attached together 'temporarily', the fact that the circles and oval are attached to the card permanently, should mean that it will all stay intact. So far, so good!