The stem of a verb like ᐊᐴapuus/he sits cannot be broken down into smaller units in which we could identify another stem. Such a stem is called a primary (simple) verb stem with only one element.
In this example, the stem is apu, followed by the third person ending (or inflection) -u.
APA:
Junker, M.-O., & MacKenzie, M. (2013). East Cree Word Formation (Southern Dialect). In The Interactive East Cree Reference Grammar. Retrieved from [URL]
MLA:
Marie-Odile Junker and Marguerite MacKenzie. East Cree Word Formation (Southern Dialect). In The Interactive East Cree Reference Grammar. 2013. Web. [date]
[URL] = website address, beginning with “http://” [Date] = the date you accessed the page, styled as follows: 13 Dec. 2015