While sauerkraut and kimchi ferment best without air - and thus in a fermentation pot with a lid - misos is different. They need the oxygen and weighting is easier in a conical pot. Therefore, these fermentation pots are particularly suitable for misos. This fermenting pot from German ceramics workshop is available in 3  different sizes.
 
Making miso yourself requires koji and the right pot. Then little can go wrong. Since miso has to be weighed down during the fermentation time and the weight of the weight corresponds best to the miso's own weight, this is also a predetermined breaking point in production. How do you pack that much weight evenly onto a jar - with a miso pot!