To start, somewhere on the sheet is the number 1 with an instruction like
"---1-->". Find the number 1 and do that fold.

Doing this fold causes the two pieces of the second instruction to line up properly so you can now read instruction #2. Do fold #2. Doing this causes instruction #3 to be readable so you can now do fold #3. Etc.

Each instruction appears right at a boundary between two layers. This guarantees that it stays unreadable until you are at the point in the model where you are ready for it.

There is no need for dotted lines to clutter the page: you must make each fold exactly so the next instruction is properly aligned.

The "Challenge" version of this would have no descriptive instructions at all. Just broken up pieces of numbers. You would have to experiment and find the sequence of folds that makes all the numerals appear in order. When they do, you're done! See if you can guess what the thing is that you have made.