Best way to block 100% wool

Up to this point everything I’ve knitted was either a blend or acrylic so didn’t need to block the item.
I’m finishing a 100% wool sweater for my daughter that is stockinette and reverse twist left rib.
I don’t want to risk stretching it as she has a pretty small figure and I’m concerned it would be too big for her if I accidently pulled it a little too much during the process.
Thanks in advance for your advice.

You don’t have to stretch anything to block it, usually you just wash it and lay it out flat to dry, patting into shape with your hands. There are different degrees of block ranging from wash/dry to stretching out a lace shawl to the max and pinning it. You don’t have to do anything but the wash and dry with about 90% of what you knit unless you do a lot of lace.

Some yarns tend to ‘grow’ when blocked so you’ll need to block it to the size you want whichever method you choose. So get out your tape measure.