How are solid state batteries manufactured?

Recently there has been news about advancements in solid state batteries, specifically for electric vehicles.[1][2] However I can't seem to figure out how they're made. Is it cost or are there specific manufacturing processes that only companies like Toyota and Nissan can do? [1]https://www.theverge.com/2022/4/8/23017045/nissan-ev-solid-state-battery-yokohama-plant-2028 [2]https://www.caranddriver.com/news/a38711469/toyota-solid-state-batteries-2025/