First, an oval shape is done with the same method. Make sure your s.a is small, like 1/8" otherwise you'll have to cope with a lot of pleats. Turn under with the needle or damp toothpick only a stitch or two ahead, no more. In applique, your thumb that is holding the fabric is your best friend and kept close to where the stitch comes out. This gives you a lot of control.
Sometimes, I use the shaft of the toothpick near its point to roll under the s.a and smooth it out. In that case, I sort of lift the s.a up a little with the toothpick rather than just trying to shove it under with the point. The toothpick is great for smoothing out by running it backwards and forwards to smooth things out. Gentle is the way to go.
You just know these ingredients are going to taste good together. My little soapbox rant is how the food companies are reducing the weight of ingredients while still charging the same price. As though we don't notice! Looky here, a 250g (8oz) block of chocolate is now 200g. As if I wouldn't notice that.
No Bake Chocolate Hazelnut slice.