You do not state the purpose of your study. Work/time studies can be controversial and give negative effects if not properly organized and presented/explained for the organization affected. A lot of literature and studies originated in the periode 1940's to 1970's. After this methods leaned more to human development and group organizing.
Suggestion of checklist:
Purpose and targets to be defined
Timeframe to be decided both for initial check and later rechecks and and development checks
Timeframe and type of for actions to result from checks
One practical methode for the analysis often used is defining all actions to be analyzed (example for warehose: packing of goods, picking items, registering of sending data etc. etc), then registering all people involved in these actions, then establish a mathematical 'non systematic ' (numbers out of hat or existing tabels for this purpose) time list used to visit and check the activities of each single person at that time.
The idea is that this repeated a sufficient amount of times and summed for each activity will give a 'neutral and statistical' picture of the work distribution.
If improvements are the purpose of the analysis the more direct (Scandinavian) approach could give better results in all aspects: ask the employees directly, either to evaluate their time distribution themselves, or to give their three to five suggestions on what single changes they thought would give the best gain to the process and company within their activity area.