So my first tip is this: fabric washable glue.
I use this stuff everyday. Just a tiny dab though because I’ve heard it can gum up ya needles. I use the Sewline brand (colour blue – it dries white / clear and washes away), and find its great for those fiddly jobs like clothing size labels and for when you are topstitching panels of fabric together where you can’t see both layers of fabric and if pinning would shift things (like in the picture).
I love this stuff
(this blog is in no way affiliated with Sewline and I received no money or product for this tip and tricks)