Qliksense by nature it has ad-hoc report creation capability. you can grant Developer / Contributor role to the end user or BA so that then they can able to create ad-hoc reports their own way using existing app/app object.
simplest way u can grant contirbutor role to then end users for creating their own report. (i.e: edit/create report role within app) after that u can add all required dimension & measure as master item so that they simply add fields into their chart objects (i.e: if we add dimension & measure into master item then they not required to write all expression)
Check this article as well,