What is the difference between timeboxing and time-slicing? From what I can tell, it is the same concept, but timeboxing is applied to project management and time-slicing is applied to scheduling algorithms. Would it be wrong to talk about timeboxing a process?
You are right in supposing that timeboxing is applied to project management and time-slicing is applied to scheduling algorithms. Additionally, the line between the usages of the words is never trespassed. Google brings up one result for "timeboxing the process", in which the "process" turns out to be packing clothes. There are six results for "timebox the process", but those processes also turn out to be either project management-related or shopping related.
Most words are popularly used in more than one context, but in this case (as in many cases when you're dealing with new words), it looks as if timeboxing has so far been almost absolutely restricted to the context of project management. You can go against the flow if you want, but be prepared to defend your decision to do so!
Time boxing can have a negative connotation since it implies that the scope of the task is being scheduled or limited for a reason. Time slicing simply limits the continuous use of a resource, but does not imply a limit on the total usage of a resource.
Busy people might time box a task, conversation or meeting because it might deliver diminishing returns to go beyond the time allotment and so deliberately ending it will, in their mind, save time and maximize results.