Texture is created in so many different ways in art journals that I think it’s important to remember that texture can be visual or it can be tactile.
Visual texture is created by using multiple layers of stamps, journaling, paint, or other media.
Tactile texture can be touched and creates another dimension in your art journal. Tactile texture invites the reader of your journal (be it just you or someone you are showing a page to) to touch the page. Regular gesso can give some texture, but if you want some nice, thick impasto texture, grab some Super Heavy Gesso (I use Liquitex, but many brands make this product). If you smear some Super Heavy Gesso through a screen or grid or other stencil, it should hold its peaks and valleys. Don’t forget, gesso doesn’t have to stay white. Gesso is also a paint extender, and adding a little bit of acrylic paint can give your gesso a whole new purpose!