Create Minecraft furniture with Command?

I have often seen videos in which YouTubers have furniture with commands. I'm relatively familiar with commands, but how can you create something like this yourself? So your own creations with a command block. I don't want to create ready-made commands but my own!

Which YouTubers did you see that?

SparkofPhoenix or Logdotzip

Are you sure these YouTubers aren't using mods?

100 percent In addition, you can do a lot of much more blatant things with command blocks

Unfortunately, I personally don't know exactly what you mean, but I could imagine that you will find what you are looking for in this channel:

https://www.youtube.com/...cMakistein

As far as I know, this YouTuber also does a lot with commands.

The following is of course not a tutorial specifically for furniture, but maybe you can learn the "basics" from the custom models here

So, that would be an example that I saw on YT. Mount a frame with a dark step (blackstone) on a quartz block so that it is facing up. Behind the frame (click on the block side that the frame is on) a white banner.

Another possibility would be an iron trap door on a funnel cart (you have to use rails and pistons), which would then look like a stove

Sorry but have a look at my question xd… I know how to do it all decoratively I have been playing Minecraft for a long time, but I would like to know how I can do it with command blocks so that it looks neater like here:

However, I would like to create this command myself

Sure, I just wanted to show that you can do cool zeucg without commands.