How do we go about landing page creation for specific product promotions?

You can create static pages with content and pictures. StoreHippo provides a static page editor that you can use to customise static pages at your end. For product-specific promotions, you can banners and sliders and redirecting the same to specific products. 

Please follow the link below for adding or editing static pages:
https://help.storehippo.com/topic/pages 

Follow this link for more details of banners and sliders:
https://help.storehippo.com/topic/slides
https://help.storehippo.com/topic/banners