This actually explains it quite well ...

https://en.wikipedia.org/wiki/UEFA_E...ying_play-offs

But put simply it looks like this, 8 of the 12 League B teams are currently in qualifying positions, which means the remaining 4 will play in the playoffs.

Bosnia v N.Ireland & Wales v Slovakia, with the host of the final being drawn.

Things can of course change but 5 of the 12 seem certs, Ukraine, Russia, Austria, Czech & Turkey.

There are therefore only 6 remaining permutations for Wales:

either away to Bosnia, Denmark or Sweden or at home to Slovakia, Ireland or N.Ireland.

Lets hope we win both games and Croatia beat Slovakia so that we can avoid the need!