Locking the teacher content.
If you want your students to work on your slides, you should work on the master (now called theme).
If you use Google Slides for assignments or if you wish to share your file with other users to work on, but want to prevent students or collaborators to move or delete something by mistake, you can add your “do not touch” content on the master.
Prepare your texts and images as you usually add them on the slides. Once you have your content ready, select it all, cut it, go to Slide > Edit Theme, right click on the layout, duplicate it and paste what you cut from the slides. (Choose keep source formatting when pasting.)
If you wish to add placeholders for students or collaborators to add their texts or answers, now that you are editing the master it’s the time to do so: go to Insert > Placeholder > Body text or subtitle placeholder. Insert as many placeholders as you need.
Once you are done, close the master, right click on your slide and select Apply Layout and choose the layout that you just created.
Here is the video of the process.
I’ve used one of the Digital Notebooks for the video, but you can use any template!