I am trying to create a 4 sided polygon.
Top is 26 1/2’
Right side is 3 1/2"
Bottom is 26 3/4"
Left side is 2 1/8"
I believe the angles (as close as I can measure them) are:
Right side 20 degrees
Left side 25 degrees

Mathematically, you will end up with a more accurate model if you measure everything ordinately.
i.e. rather than measure the length of each side, measure the XY points of each corner.
Scribe/draw 2 (perpendicular to the 26.75 base line) lines on your part, and measure X & Y dimensions.