Stitch up through 1 and then skip a single hole and go down through 2.
Stitch up through 3 and then skip another hole and down through 1.
Repeat this process skipping a single hole each time.
The benefits of backstitch on evenweave is you can use a higher count fabric. For example you can stitch a 14 count pattern exactly the same size on 28 count fabric (28 is twice the count) and there will be less obvious holes in the fabric to distract. Some people find this more visually pleasing. It also lends itself easily to work with fractional stitches as the fractions can be stitched into the holes that have been skipped.
The downside to this method is it is easier to miscount your stitches and not skip a hole accidentally. This can lead to throwing your stitching out.