When you're done, remove the flanges, pull the top layer of cloth down, and make sure your nipples aren't directly behind the slit. Go back to work, ...
If you've got a baby, and work outside of the home, or otherwise need to be away from your kid from time to time, you're probably already acquainted with breast pumps. While being able to produce tasty, nutritious baby food with one appliance, and body parts you already had on hand is a good thing, it's not always convenient. Being able to easily eat, type, or read while pumping makes the task a lot more pleasant, and making a hands-free setup is simple. There are bands and bustiers you can buy for this purpose, but they need to be used over nursing bras, which I prefer not to wear, and putting them on is an extra step.
Buy or find a full-coverage bra with formed cups. Basically, what you want is something with firm, foam cups with a layer of fabric over those. A lot of 't-shirt bras' would work, and a lace overlay would be good, too. It's just important that there be two layers, and the bottom one needs some structure. Find some scissors, too.