With right sides together pin the side panels to the front panel – ensure you line up the hem and line up the pockets. Stitch with a 1.5cm seam allowance. Press the seam flat as its been sewn and then press towards the front panel – press the seam allowance all the way onto the bib of the apron.
Avoiding the bib part of the seam allowance, trim down the under seam allowance to 6mm (you will need to cut into the under seam allowance near to where the side and front panels meet).
Fold and finger press the untrimmed seam allowance down over the trimmed one and pin. All the raw edges should be underneath the seam.
Fold under the raw edge on the bib part of the apron and pin. Stitch all along the seam close to the edge.