Originally Posted by sharon b
I would square up the inside square , to make the edges even and that also should help bring the size down to match the outsides that you are trying to attach.
Before you cut the square, make sure that the triangle pieces from the alternate block will mate up properly. They form the continuing and interlocking part of the grid. When the triangles are not the right size, it disrupts the flow of the interlocking line. I have done this pattern a few times and love it. Would not consider this a beginner pattern. So good for you for trying your hand at this.
Here is one of mine that shows the flow I was talking about.