A stack of pieced units sits beside the machine, pressed and waiting. The square ruler and the rotary cutter are within reach, and the question that arrives is not how to trim, because you already know how. It is which pieces actually need it, and to what size.
Marilyn, of Good Enough Quilting, works through a pile of quilt as you go blocks in real time and says her decisions out loud as the ruler goes down. This is session two of her scrappy bricks and stones quilt, so the units are already made and the trimming is the whole job.
Watch what she looks at before she cuts, rather than the cut itself. Trimming to the number on a cutting chart and trimming so the edge can survive being joined to the next block are two different jobs, and quilt as you go is where the difference shows, because every block is squared on its own before it ever meets a neighbor. Hearing someone decide it out loud, block after block, makes the criterion clearer than a diagram does.
If you are new to the method itself, our own guide covers it from the first block to the last join: quilt as you go, the complete guide for beginners.
Credit where it belongs: the tutorial is by Marilyn, on the Good Enough Quilting YouTube channel.