'ways which' is an acceptable phrase in written English.
You can use it when referring to methods, techniques, or approaches. For example: "We discussed the different ways which can be used to reduce our carbon footprint."
People behaved in ways which were inconsistent.
I've read it now both ways, which I recommend.
The artists all thought in similar ways, which crushed innovation.
They are acting in ways which Africa really needs now.
Consequently, indium can reach humans mainly by natural ways, which could result in a health hazard.
Among the ways which restoration success was evaluated, vegetation structure (e.g., abundance, density, etc).
Parwana's payback comes in more subtle ways, which are nevertheless shattering.
But these elements fit together in ways which never properly repeat themselves.
People understand a marriage in ways which they do not, quite, understand a civil partnership.
There were other ways of knowing the world, women's ways, which he treated dismissively.
In the past governments have acted in ways which made things worse.
