If you look at the Crumbliser product page, one of the photos shows them soldered together.
You should be able to see that the gold plating continues around the edge of the Crumbliser PCB – this give you a surface to solder to. If you overlap the Crumbliser and the strip by about 1mm, with the Crumbliser on top (you want a bit of the solder pad on the strip still showing), you can apply a little solder to make the joint. Once the first is done, the others will be easier as the two pieces are now held together.
There might be a small amount of solder on the strip already, but adding a little extra fresh solder will introduce some flux and help the solder flow nicely.
I hope this helps. If you need any clarification, please don’t hesitate to ask.
All the best,