Fitting on myself with nobody to pin the back — what actually works when you sew alone?

Make the toile close with the opening at the front, even if the finished garment opens at the back. You can then adjust the back on yourself by pinching and pinning at the side seams and shoulders where your hands actually reach, then transfer those changes to the paper. Fighting a back opening on yourself is how people conclude that solo fitting is impossible.

Phone on a tripod shooting video, not stills. Set it behind you, record thirty seconds of you standing normally, reaching forward, and lifting your arms, then watch it back frozen at the moments that matter. Photos catch you posing, video catches your actual posture, and back fitting problems are almost always posture problems. It changed more for me than any tool I have bought.

The padded duct tape form gets recommended constantly and I want to be honest about it: mine took an evening, cost very little, and is genuinely useful for checking hems, drape and balance. It is not good for pinning fit adjustments, because it does not move, breathe or slouch the way you do, and a garment fitted to it was tight when I reached forward. Useful tool, not a substitute for fitting on yourself.

Fit in the flat pattern before you fit on the body, and most of the solo problem disappears. Take a garment you already own that fits well across the back, measure it flat — back width at the armhole, across the shoulders, the depth of the armhole — and compare those numbers to the finished measurements of your pattern rather than to your body measurements. Nine times out of ten the discrepancy is sitting there in centimetres before you have cut anything.