How to stitch headband for baby girl

Elastic
15" + Seam allowance 3/4"

Head Band
length 27" to 30 " + Seam allowance
width 2*(width of elastic) + Seam allowance

Bow
length 2*(2 1/2" to 3")  + Seam allowance and width 1 1/2" + Seam allowance
OR
length 2 1/2" to 3"  + Seam allowance and width  2*(1 1/2") + Seam allowance