Difficult Area On Cheyenne Dress

I have designed the Cheyenne inspired dress to have cut outs on the back with shapes taken from my print. I didn't really know the best method in how to create this look so I began by:

• Cutting out two medium size pieces of calico and the shapes which were taken from my print.
• I then hand stitched the two pieces of calico into a triangle shape.
• I then placed each of the shapes on to the calico. I made each shape go smaller so that they would fit into the triangle.
• I hand stitched around each edge of the shapes which touched the calico so they were all attached.
• This method didn't go to plan and didn't look like a professional finish. I am going to try out another method and see if I can create a neater finish which fits in with the concept of the Cheyenne dress.