When adding a few stitches

When adding a few stitches like your design, I like to do either the knit (or purl) or cable cast-on. To do a knit (or purl) cast-on, insert your needle tip as if to knit (or purl), wrap yarn, pull stitch through loop on holding needle but do not drop that loop on the holding needle. Place newly created loop back on to holding needle. Insert working needle tip as if to knit (or purl), pull loop through and place back on holding needle. Continue until you cast on enough stitches.

For the cable cast on, insert your needle tip in between the last two loops on your holding needle. Wrap yarn and pull it through in between the two loops. Place this new loop on holding needle. Now insert your needle tip in between this newly added loop and the loop next to it. Wrap yarn, pull it through and add this new loop to your holding needle.

Me personally, no matter what I do, I find a slight looseness in the area where I have added new stitches. Either this blocks/washes out if it is not too loose, or I do an editing afterwards which covers it up.