"Right!" you say. "You've had enough of my lecturing. How about a quick demonstration of summoning?" You hadn't planned on a demonstration, but the way the students sit up more attentively at their tables, you're glad you're doing it.
You rifle through your collection of metal patterns. "Aha, here we go." You brandish one card, its pattern a deep forest green to your synesthesia. "I'll summon a small patch of pattern-sensitive moss. It's remarkably common across universes."
You clear space on your desk. The students sit up in their chairs, craning their necks for a good look at what you're about to do.
You clear your mind and lift your pattern.
Summoning is like feeling around in a drawer for a pen and hoping you don't cut yourself on scissors while you do it. The pattern wriggles in your mind while you reach mentally across dimensions, until—there! The moss you're after.
A glowing point forms above your desk, then widens into a rip in space. Light red moss spills onto the desk surface, covering a dinner-plate sized patch. You tighten your hand. The rip closes.
As light from a window falls on the moss, it darkens. The sunlight in a meter sphere around the moss vanishes. While you follow your backlash routine, the moss gives off a steady green glow within its sphere of darkness. "The moss is actually converting sunlight to pattern energy to sustain itself and giving off that light as a byproduct. When night falls it'll go dormant and I'll dispose of it."
You walk the class through the techniques you used. Pens fly across paper as the students take notes. They couldn't tell you'd improvised the demonstration on the spot.
Success!