SAHM - kids all in school, need a new routine

Hi, I'm a SAHM to 3 kids, ages 8, 6, and 4. My 4 year old started prek in September. I'm having a hard time adjusting to the new free time I have and really missing the old times of caring for one or more of my kids all day, every day. I thought I wanted a break from them until I got it. Now that it's been a few months of trying to adjust, I'm trying to push through the depression and find new things to do in the hours they're gone at school. I can do housework freely now, which is nice, but there's some days where I have too much time on my hands. Anyone who is/was in a similar situation, I'd love to hear from you whether it be advice or whatever. Thank you!