Lucet braid is made using a "lucet", which is essentially just a forked stick. It is therefore possible to make lucet braid by using any twin pronged implement, without needing a specific tool.
A figure 8 of yarn is passed over the prongs and then the yarn is passed again over the first prong. The bottom loop passes over the top one and then the yarn is passed around the second prong and the bottom loop brought over the top. The process is repeated and the square section braid appears down through the hollow tube after a while. Lucet braid can be made to any length.
Although we have little surviving evidence of the resultant braid, the archaeological record has thrown up a number of objects which may be lucets. While there is enough evidence to suggest that lucets were used in the early medieval world, they are unlikely to have been common.
Inauthentic modern lucets
Flat wooden lucets with a hole in the middle for the braid, a style frequently used by reenactors, are too modern for the Early Medieval period. This style developed in the Renaissance and may not be used in the Vikings Society.
A detailed datasheet setting out the evidence for lucets and lucet braid in the early medieval period is available in the Lucet datasheet.
Credits: with thanks to Dave Constantine and Jennifer Bray.