Grab a bowl for your marinade. Zest your orange and add all of the zest to the bowl. Then cut the orange in half and add all of the juice as well. You should have at least 1/4 cup orange juice and anything more than that is just fine.
To the orange mixture, add soy sauce, vinegar, honey, sesame oil, ginger, coriander, and garlic. Then add Sriracha to your liking. If you like heat, I'd start with more like 3-4 teaspoons of Sriracha and add more if you like. Whisk the marinade so everything is combined.
Take the flank steak and slice it across the grain into about 1/4" slices. It helps to pop the steak into the freezer for 20 minutes or so before hand. Place steak in a zip-lock bag and pour the marinade in. Swish it all around and pop the bag in the fridge. It's best if it can sit for at least 4 hours.
When you're ready to get cookin' preheat your grill. Then take your skewers (pre-soaked if you're using wood/bamboo ones) and thread on the strips of meat, just like you're stitching. You don't want them to be too smooshed on there. In order for them to cook evenly, stretch the meat out a bit.
Place them on the grill. These cook really fast. They should only take about 3-4 minutes on each side. Flip half way through.
Serve immediately - they cool quickly. Be sure to have the rest of the meal ready before these hit the table!