From Kwik Sew
Using pieces of fabric larger than your pattern pieces, cut the interfacing to the same size as the fabric. Fuse the interfacing to the wrong side of the fabric. Place the pattern pieces on the interfaced fabric and cut out the pieces. The results will be perfect every time.
Till now I used to cut out all the pattern pieces, including interfacing and then fuse them together. Kwik Sew’s method is great