I would love to know how other people do short practices. I don’t seem to be able to. One asana does not a practice make, in my opinion. Doing a downward-facing dog between the shower and getting dressed is flossing yoga.
[Digression: My friend Jill made a comment once about “flossing yoga” by which she meant, it turned out later, the kind of yoga you do while flossing your teeth. Tree pose, for example? I misunderstood her explanation and thought of flossing yoga as any of the intermittent yoga poses you do during the day, like when you’re reaching for something on the floor and wing up into Ardha Chandrasana (Half Moon) against the kitchen cabinets, and then of course you have to do the other side to even things up.]
This morning I turned off the alarm and thus overslept enough so that I only had 25 minutes for yoga and no more. Even if I don’t chant the Invocation to Patanjali (quietly so I don’t wake up my husband, who will think I am weird, or the dog, who will want to go outside), I really don’t feel right just starting right in. I need to do some little centering thing, even if it’s just hands in Namaskarasana (prayer pose) and eyes closed, breathing quietly. So then I think to myself, “Three poses only! That’s all the time there is!” Adho Mukha Virasana (downward-facing hero), Adho Mukha Svanasana (downward-facing dog), Uttanasana (standing forward bend). But then I find myself adding something more. “Oh, I’ll just throw in one quick Trikonasana (triangle pose).”
I’ve been very well trained by my teachers, and so I can’t just stop. I have to do at least five minutes of Savasana (corpse pose). Nor can I leap up from the mat after that – there’s the returning-to-the-world seated pose for a moment, where I feel grateful for the day, and promise to practice compassion.
Before I know it my time is up, and maybe I’ve gone over by 5, 10, 20 minutes, and my ride is waiting, or I have to go take a speed shower instead of a leisurely one, or do whatever else is pulling me toward the day.
What about those short practices? What’s in them? Sukhasana (easy seated pose), Trikonasana (triangle), Savasana (corpse)?
Practice Notes 
Sun salutations, if you do a series of them, gives you a great deal of benefit when you have little time. Letting your breath dictate the length of time you stay in any pose means that by the time you’ve hit three salutations you’ve hit a very nice rythm (usually it takes only one, but repetition gives it an even more rolling rythm). You don’t get any twists, but do get prayer pose, that arms-over-the-head stretch, ragdoll pose, plank pose, cobra pose, and a few others. I throw in a downward-facing dog as well. So starting from quiet the sequence builds energy and momentum until you’re back up on both feet, arms up and back arched, and then slide your hands back down into prayer pose, for a return to the quiet.
Sun salutations done this way do what coffee supposedly did, as claimed in that coffee ad of the 90s: Calms you down as it picks you up. You get to feel calm and invigorated by the end of your allotted time.
At least it works for me.