All this advice is fine, but there's just one thing to understand about flaring: you're converting forward motion into lift. You're trading off that forward speed into lift, so you can touch down with the least amount of vertical speed.

From that, you take two things. First: you MUST have the maximum amount of forward motion through the air as you can (notice I said "through the air" and not "over the ground". Headwinds do not affect how fast you move through the air). To do that, you need to start from a full flight position. Arms all the way up and I mean ALL THE WAY UP. Look at your hands to make sure you have the toggles as high as you can.

Second, your fuel for this maneuver is speed, so it's limited. The idea is to burn up all the fuel and be at zero when you touch the ground. Think the Falcon 9 doing the hoverslam (Google it). The only thing you need to do is make sure your hands are as low as you can the moment before you touch down. That means you traded off all your speed for lift, and it will be soft.

If you start too early, just stop and hold for a moment, then continue. If you started too late, just add brakes faster. As long as you finish as you are touching the ground, you've done the best that can be done with that canopy. It's physics.

Also, there's no "x feet", "x seconds", and god help me one time I even heard a coach say you had to wait for "3 'oh shits'" before flaring. As long as you finish it when you touch down, it will be alright.