Well, you could create a custom basal, called, for instance, PostMeal, and that could have a basal segment that would be, basically, an extended bolus. Then you could switch to the PostMeal basal, then out of it later in the day, when convenient. I assume it would be exactly the same as a normal basal except for your “extended bolus”).
There isn’t an easy way to automate it. You have to either have a meal time that is always the same so you could have the post-meal basal (extended bolus) programmed, or you would have to set alarms or remember to turn it on or off.
So the best way may depend on if your schedule is consistent, or if you don’t mind alarms and reminders.