Problem: baby likes to talk to grandma over video call, but the little one also presses every single button there is on the touchscreen, resulting in (at best) hanging up or (at worst) the phone being left in some indeterminate state.
If you have a transparent case you can probably just flip it over and cover the camera-hole with some tape, but otherwise you can build your own baby-safe box like this.
Bubble Wrap[e]. You can use anything that is slightly flexible and has good friction.
Put some of the adhesive velcro on the short sides of the transparent lid and on the back of the bamboo lid. Then cut the cable ties so you get strips of velcro of the right "polarity" to hold the back and front together. Finally, slap a rectangle of bubble wrap in the middle to hold the phone in place without crushing it.
Call grandma, stick the phone in the box and strap it down.
Hand over to the baby and you are done.
