So how can you start chunking? Start small until you get the feel of it. Pick a single task, perhaps your weekly report. Set aside the 30 minutes you know it will take. Close your door. Put up a sign that reads "Genius at work" or something like that and then concentrate on the report and nothing but the report. Ignore the phone.
Don't check email. Just write the report. After about two weeks you'll notice how much more quickly you are able to get your report done.
When you're ready for the next phase, set aside a chunk of time for another activity. For example, instead of interrupting whatever you are working on to read each email as it comes in, set aside a specific time to tackle a chunk of emails. One manager I know reads all her email at the beginning of each hour and then ignores it until the beginning of the next hour.