Inside corners (complex)

Inside corners on a triangle are much easier. Using reverse appliqué gives a triangle inside corners. 

What if the triangles are a part of a larger design and there are other fabric layers involved?

Here's one in which the triangles are part of a curvy line. If the background fabric on the left is used for the complete design, then the triangles on the right would have an edge and two angles on top of it. In order to keep the triangles looking crisp, they need to be reverse appliquéd on both left and right. Hmm.

Here's the trick.

Draw out the design, clearly labeling the layers (switch green for red in my sketch).

Cut the design. Other layers can be cut separately to keep the lines complete.




Appliqué the layers in order. Find a nice quiet spot on the curvy line, cut the seam allowance right to the sewing line and switch the foreground and background fabrics. There will be a slight bump when the lines cross, but it will be difficult to see if done neatly.

This technique allows both triangle sections to be done in reverse appliqué, so the points can be sharp.