I pull the yarn through the last stitch so it won't unravel and then put the tapestry needle under the bound off edge of the first stitch and kind of weave in the ends. I don't know that I use any particular 'technique', but it does get rid of that little gap.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog