When we decided that baking our own bread was going to be a serious venture I had a hunt for some bread tins. All I discovered was that they are ridiculously overpriced. So, staying true to our family roots (being super cheap and not liking to part with hard earned cash), we opted for making our own. After some trial and error we found our groove and are pretty stoked on what we have created - and partly copied from the Germans.
To start, grab some untreated wood - we used pine, 9mm thick and 90mm wide (http://www.onlineconversion.com/length_metric.htm) Cut two small sides, 100mm in length and two long sides, 250mm. And start nailing those bad boys together!
Once you have nailed your boxes up good and tight, you want to give them a generous slather in cooking oil and a nice hot pre-use cook in the oven. Heat them up at roughly 200c for 20min. You'll want to re-oil again after they cool and before every use.