I wanted control over the INNER edges of at least two of the inner 'edges'. I created two horizontal lines on the squedge with tape where the edges of a couple of the strips are sewn. That way each time I line up the squedge I can check the angles between the upper and lower edges.

I found that with my horizontal lines I can check how well I pressed my strips and get better angles.

See the photo below. (Pardon the ugly spots leftover from using duct tape on the back in the past!)

Love the topper, Phillips Fiber Art has a great video on how to may this topper.

Very cute, great job and thank you for sharing
Have a Blessed day
Ellen