Bassleri should be handled like other large Epipe frogs including silverstonei and trivittatus. These species are usually hard to get breeding but once they start they become very prolific or at least very consistent. Large frogs need large vivs, epipes are leaf litter frogs, so large squat vivs is the best choice. see Mark's post above, 40 gallon tank, that's what we're talking about.
Leaf litter, slabs of cork bark, driftwood and some densely planted areas will all contribute to the frogs feeling secure in their enclosure. All 3 of these species are shy frogs and need places to dive into for cover and hide from each other. Like other Epipes there will be a pecking order where the stronger larger frogs bully the others, so be watchful, especially with smaller males, they may need to be pulled. Again as Mark suggested keep them in pairs for best results.
Another important ingredient to breeding these frogs, as with all Epipes is water. Large water features like pools or running stream of water should increase the likelihood that the frogs will reproduce. Anyone who has idle pairs without a large water source should consider new quarters for the frogs.
BAssleri is one of the Epipes that can change color intensity with mood and social place. I've seen this with younger males that have reduced coloration and almost appear to be females. The boldest alpha male will almost always be the brightest colored frog in the group.
Hope this helps
Eric