I am an Owl who is forced to be a Lark because of my day job and I am also an Obliger, as defined by your book. I arrive home late and tired from work but am still sometimes able to write after eating dinner and before going to bed. Those evening sessions are difficult, however. Other family members have the TV going or demand my attention. Mornings are not a creative time for this Owl, although I have been forced, due to time constraints, to dole out some writing time during the hour before leaving for work.
I find that writing during the day works best for me. I schedule my breaks and lunch so that I can, on most days, spend fifteen or thirty minutes writing creatively. Generally, that works for me but often interruptions and work deadlines prevent these creative breaks. But, I try. . .
The one for-sure thing that keeps me writing is accountability to others (The Obliger). Medium writing prompts are fabulous incentives for me to write, as is making a public statement or commitment on Medium that I will write every day or every week, etc. I feel compelled to write when I think others will notice if I don’t and even if they don’t. No one ever calls me out for not writing but just having made the statement that I will write obliges me to write.