Short Lessons, Time Boxes- How?????

I am struggling to figure this out. I really want more time in our day for fun things like art. So I tried using a timer for each of my girls in their skill subjects. My oldest struggled with it the most. For example, she is in 5th grade and I gave her 30 min. to do her math. I told her do as much as she could and anything she didn’t finish she could do later, no pressure. The problem is I don’t give her a lot to do. She had a total of 10 problems yesterday. She knows what she is doing and applies herself. She is just not the fasted at it. The timer also stressed her out no matter how much I tried to reassure her. My biggest stuggle is that it feels like public school to me. I hate interrupting my child’s thought process with a “bell”, especially for things like reading and writing. Also putting a time limit on instruction time (explaining a math or grammar lesson) is annoying. Some things just take longer to explain.

My middle dd is my daydreamer and she would just forget to set her timer. It did not stress her in the least lol.

I tried using the timer for our other subjects. It really bugged me when the timer went off while we were talking about the habit we are working on, or in the middle of a sentence while reading, etc. I would still finish up the lesson or paragraph, but the timer going off drove me nuts!

I thought about just watching the time instead of setting the timer. But truthfully I would end up forgetting then feel frustrated. I thought about giving them a block of time to do their work, instead of a time for each subject. But how will they know that they have spent too much time on one subject and won’t have time for other subjects?

So how does this work in your house? How do you make sure lessons are short?