Once single-item speed plateaus, the next gain comes from chunking: combining two or three items into one pre-built scene instead of encoding them one at a time. Chunking is why experienced card memorizers can process a deck in under a minute, they’re not picturing 52 things, they’re picturing roughly 17-26 combined scenes.
Practice by taking pairs of items and forcing them into a single, single combined image (not two images side by side) before moving to the next pair. It’s a different mental motion from linking two separate images, you’re compressing two ideas into one visual unit from the start.
Try it below with items presented two at a time.