no experience, but I feel like this makes it easier. If you've already discussed the no shows and warned them about it, I think something about 'we've discussed xyz issues last month/whenever, and unfortunately this has not significantly improved and we have decided to let you go."
Heh...reminds me of me old supervisor days...we had a probationary period where we could pretty much cut someone for any justified reason immediately while they were on probation. When they came in, I spent like an hour going over all the rules, and had them sign that they understood the rules. In that list, was breaks (3 15 minute breaks on 2nd shift, no 'lunch' 1/2 hour). A few weeks later, I hear from one guy's partner that he is taking long breaks, so I watch him. 20, 25 minutes he's gone. I pull him aside and say "remember we talked about 3 15 minute breaks?"...he claims it was accidental. I respond "understood, but remember, you're probationary, you're being evaluated as to whether you can be trusted to do what you need to do. With close to 50 direct reports, I can't watch everyone and monitor breaks. I expect you to be responsible on your own. As such, I expect that we won't have to revisit this issue, and there will be no more long breaks. Whether you need to set a timer on your phone, whatever, YOU need to manage it" He understands.
Week later, I follow up, he takes like 20, 25 and 22 minute breaks. I pull him up at the end of the night and say "remember we talked about this?" he starts to get nervous, and I tell him he's done. He starts wigging and telling me he'll only take 2 breaks, it'll never happen again, etc. I tell him that it's not about the time, it's about the fact that after being talked to about it, it didn't improve, so he's shown me he's not reliable. "I'll only take one break, I won't even take a break". Didn't help.