The main idea here is to have a center raised/beveled line and then stamp some pattern on one or both sides.
It starts with drawing the two parallel lines with a compass, cutting them with a swivel knife and then choosing between a smooth, textured or figure carving beveler.
Here is the video (in two parts):
And here are still photos of the samples that were made or shown in the video:
In the following small journal cover, the border stamp was also used against a beveled edge, but it was not a center line design. (The design was drawn on a phone using the Sketcher App by Valentin Myamsin)