Shifty linen needs to know who's boss! Show it by interfacing all of your curved pieces as soon as they've been cut. I either stay-stich using a 1.5mm stitch length or I use this iron-on bias tape.
The tape itself is non-rigid, which allows for some movement, while the stitch running through the centre of the tape acts like a stay-stitch. It's so useful for bias cut edges which stretch out before sewing or can drag over time.
Place the coated edge on the wrong side of your fabric, placing the stitched centre 1-2mm inside your seam allowance. Cover with a press cloth and press with a light steam for 10 seconds. Don't move your iron around but maintain an even pressure on each part of the interfacing. Allow it to cool so that the glue can set properly.
Don't buy too much interfacing at once. Buy just enough for your next two or three projects becasue the glue deteriorates over time and it becomes less effective when stored for long preiods.
Always test interfacing on a scrap of fabric before using it on your project.
Charcoal or White