Block and weave in ends before assembling sweater?

Im almost finished with my first childrens cardigan, Should I block and weave in ends before assembling? I Assume blocking would make it alot easier, but Im not sure if your suppost to use your tails to sew arms t body, is doesnt say you are…It just says "sew shoulder seams"
How do I do this anyways??:??

You can use mattress stitch, but to be honest, the best shoulder seam to use is a 3-needle bind off. It requires you to leave the shoulder stitches ‘live’ (so if you want to do it you have to take out your bind-off.)

I sew before I block, if I block. If it’s an acrylic sweater, then don’t bother. I suppose you could wet and flatten it out a bit, but the seaming will take care of all your curling, anyway.

If the tail is long enough to seam with, then use that–it accomplishes two things at once–seaming and weaving in. If not, I usually leave the tails until the end and weave them up through the seam.