What I meant was that if you select bottom in Both Layers, all traces made from then on will be on the bottom.
Sorry, but I must get something wrong - I can not convince the Autorouter to only place traces on one layer, no matter what I try.
Here are the files, if you want to have a look at them (hopefully it is OK to include the one Top View part I use on the breadboard - if not, I’ll remove it):