The 'tch' and 'ch' spelling should BOTH be pronounced as /ʧ/ (the ch sound, yet 'tch' often seems easier for non-native English speakers.
Full episode transcripts at www.pronuncian.com/podcast.
Nov 2016
221: Compare ’unvoiced th’ to /f/, /s/, and /t/
How to pronounce words like "thin/fin," "mouth/mouse," and "both/boat." Perfect your English fricative sounds by never stopping the air from passing through your mouth. Transcripts at pronuncian.com
12m 43s