What I did some time ago for this site (and for all sites I do this,) I grabbed a little piece of code given below, and created a page for it. This page is nofollow/noindiex; is private and has everything turned off.

I put a hash tag in front of the title so it will always be on the top of the list of pages.

The code for the little text box is all that's on the page. This box gauges the length of text that you set.

Here's the code:

<textarea maxlength="158"></textarea>

I have it set to 158 because that's about how long the SERPs descriptions are. It is best if you create a topic sentence or two that will go into that space. and when you get to the 158th character (including spaces) the little app acts as a stop.

I put the subheader in there and modified it. You will see it in the end result...