mini quilt - triangle border problem

I'm making my first mini quilt to try and improve my cutting and sewing skills. The pieced border calls for cutting a 1 3/4" square into quarters diagonally; join two quarter pieces, one red and one plaid, to make a border unit. The long sides of the trianlges are opposite each other. I cannot make this happen! How do you match up the ends? Is there a way to tell if the size of the square is wrong to begin with? The rest of the quilt went together as directed - still working on my skills, though. Oh, the directions give the option of paper-piecing with a template provided. Pattern is from: It's a Small World, by Els Feteris-Stam, and is called Baskets (Mandjes).

Thanks for any comments,
cmn2015