This article explains how to record a video on Instagram without having to press any buttons.
Steps
Step 1. Open Instagram
The icon depicts a retro colored camera.
If prompted, enter your username and password, then tap "Login"
Step 2. Tap the Home button in the lower left to view the feed
This page opens automatically upon login
Step 3. Tap the camera button on the top left
You can also access it by swiping your finger from left to right across the screen
Step 4. Tap Without holding
This option is located on the far right below the shutter button.
To see this option you need to slide your finger to the left
Step 5. Tap the button that allows you to take photos and videos
As soon as you tap it Instagram will start recording. Tap it again to stop recording.