I can only comment on the two I’ve actually designed and made, i.e Bob and Knock Out, but essentially yeah, I start off with a base shape and then build up the rest from there. It takes a while, but it means each bit fits nicely and especially as they’re robots, I think it gives them a more armoured/layered look… Well I hope that’s what it looks like anyway…
As much as possible, I use my sewing machine, so the actual parts are machine stitched into the right shape together, but then I have no choice but to hand stitch them to the actual body.
LUCKILY FOR ME, and my atrociously ugly hand stitching, the short pile of the minky I use is beautifully forgiving, and hides a lot of the stitching. As well as that, I tend to mostly use a bastardised slip stitch, which is very discreet.
I’ll be honest, in that I have literally no real idea of how to hand sew properly, I just tend to jab a needle and thread into something until it looks good :/
***I just googled it, and apparently I’m using some sort of slip stitch/needleturn fusion I don’t even know, but this is quite a nice tutorial on needleturn and sewing applique, which is essentially most of what I do…
If it’s any help, the embroidered lines I did a lot of on KO, were made using the buttonhole setting on the sewing machine, and I just made sure to let the fabric through very slowly, so the line was dense and evenly sewn.
I had a vaguely similar question a while ago, and I floundered through an answer there as well, and that can be read here.
Aside from that, the only thing I know which people might find useful is about making hands, and that post is here.
Argh, rereading this and it’s a crappy answer, but I’m still kind of really new to this. Most of my experience comes from making clothes and cosplay, and I just apply the things I learnt from that to plushies too :/