There are free plans for a knock-down workbench from The Woodsmith Shop. I didn't mention it before, because @SEMIJim
wants a different kind of knock-down workbench, somewhat larger.
I am mentioning it now, for others who may be interested. If you try to find the plans with a web search, you will find the paid version. Your web search may also turn up lots of those SCAM "Thousands of Plans" or "Ted's Plans" or variants, so watch out for them! They are a SCAM to steal your money!! If you find any of those webpages, close them quickly. Some may contain malware.
The knock-down workbench was shown and described in a television show, The Woodsmith Shop, Season 12, Episode 1. Go to the webpage below, and look very carefully below the right corner of the "Episode Preview". You will see a link to EPISODE 1201 PLANS: "Knock-down Workbench" here:
The season is still active, but once it ages out, you won't be able to download the free plans in the future. The plan files are small, so I try to remember to download and save the entire season's plans while the season is still active and the plans are still free.
You can get the plans FREE using the link above, but here is a link to the same plans, but it is for the PAID version. The reasons I am posting it here are: (1) So you can see the photos of the workbench easily, and (2) Eventually the free version will not be available, and others may find this post too late to get the free version, but want to buy the plans anyway.
PAID VERSION TO VIEW PHOTOS. TO DOWNLOAD FREE PLANS (IF STILL AVAILABLE), TRY THE LINK ABOVE FIRST: