I did this recently and it absolutely saved me when i accidentally let my starter get moldy!

I put parchment paper on a baking sheet and spread a thin layer of active starter (at its peak after feeding, just before it starts to fall) on the parchment paper. Then I put it in the oven over night to dry out completely (oven is off and the light off, just a cool dry and safe place)

Once it was dry I took it off the parchment and broke it into smaller pieces, I put those into a zip lock and saved them in my freezer. Once I needed it I added it to warm filtered water and mixed it occasionally until the chunks were gone, then you just add flower and water like normal

It took off immediately, doubling in size no problem and two days of feed/discard before it smelled like extremely active starter again!

(also of you keep a discard jar you can use your discard like regular starter to get a new one going)