Page 151 - Peter Randall "The Craft of the Knot.."

STEP 1 To start, you’ll need three cords. The cords may simply be held
together, or you can tie them together at the top. To start braiding, move
the left cord to cross over the middle cord.

STEP 2 Next, take the right cord and cross it over the new middle cord.

STEP 3 Continue making crossovers, alternating sides until the braid is
as long as you need it to be. Secure the ends, if necessary.

The Three-Strand Braid is sometimes tied with strands of different
colors. Moreover, each strand can be a pair of cords, or a group of cords.