One of my favorite ways to do this is with a make 1 increase.
There are three basic ways to execute a make 1.
1. Lift up the running thread between stitches and work it, typically twisted shut.
2. Create a yarn over on the previous row or round, then work it, typically twisted shut, on the next row or round.
3. On the previous row or round, cast-on a twisted (backward) loop on the right needle; then work it on the next row or round.
All three of these methods create identical architecture. All three of these methods can create either a left-leaning or right-leaning stitch.
My favorite way to make mirrored make-1 increases is method #2, by using a yarn over and a reverse yarn over. You may wonder if this takes too much thinking. Actually, this method requires very little thinking, other than deciding whether to work yarn over then reverse yarn over or vice-versa. Here's the principle:
yarn over, worked through the back of the loop = left-leaning
reverse yarn over, worked through the front of the loop = right leaning
You might think you have to remember which way to work the yarn over or reverse yarn over, but that's not really the case. It is obvious when you go to work the yarn over or reverse yarn over that one way will twist it shut and the other way will keep it open. You can tell this as soon as you insert the needle, even before you have completed the stitch. All you really have to remember is whether you are working rev-yo, k1, yo or yo, k1, rev-yo on the previous row or round.
In the first image (above), the increases lean outward. The right-leaning increase is on the right side of the center spine and the left-leaning increase is on the left side of the center spine.
In the second image (below), the increases lean inward. The left-leaning increase is on the right side of the center spin and the right-leaning increase is on the left side of the center spine.
In both of these pictures, I've stretched the fabric in an embroidery hoop to open it up and make the structure more visible. Normally, gaps and holes would be less obvious.
Neither method is "right" or "wrong." It is simply a matter of taste. Which one do you like best? Do that.
I should add that I learned most of this method from Candace Eisner Strick. The yarn-over method is especially handy on projects with every-other round increases such as toe-up socks or top-down raglan sweaters. Normally if you put your work down, it is easy to loose your place and not know whether you are on a plain round or an increase round. With this method, it is obvious. If you come to a yarn over or reverse yarn over, then work it twisted shut. If there isn't one, then you need to make a yarn over or reverse yarn over. Clever!