Put all devices on do not disturb and put in earbuds & appropriate music. Sometimes calming music, sometimes energizing, take no prisoners music
Firstly, I keep my phone away. I cut off any kind of distraction. Secondly, I create an environment which motivates me to focus deeply into my work. Like choosing a table or chair which help me sit upright but not stiff ; I also choose some flowers to put on my desk because seeing color in general make me happy. Thirdly, I do not look at the clock because when I look at it, I get thought like "How much longer do I have to do this? " which is not good when you focusing on something. Lastly, don't let your eyes strain too much. Close your eyes for 10 or 15 seconds between 10mins intervals, that way you won't tire your eyes.
I usually set my timer, close My inbox an put my phone on Do Not Disturb. Set my intention and begin. Once I am focused the deep work begins