For stay at home working moms, how do you keep your toddlers busy while you work and no one is available to look after them?

My 2 toddlers used to stay in the play yard while I am working from home however I noticed that it's becoming smaller for them. Recently, we customized a more spacious play yard where they can move freely and put as much toys as they want. Just make sure there no sharp and poisonous objects inside. Also, at least we know they're safe because they can't go just anywhere. Here's a photo of their original play yard before we customized it to become bigger.