Smartly pop your seal with just one hand! I found a convenient item called "Pitatto Seal Stand" at Daiso, a 100-yen shop.
As the name suggests, a stand with a suction cup for holding a seal. When you pull out the seal, only the cap will come off naturally, so you can stamp with just one hand. With this, you can receive the delivery smoothly, and you can prevent the situation that "the cap has gone missing!". The corresponding seal is Shachihata's "Name 9". If you use the attached adapter, it also supports Shachihata's "Name 6" and Daiso's "6mm mark" and "Name mark".
It's a very convenient item, but it has one drawback. Since the seal cap is firmly fixed inside the stand, it takes some time to remove it. It may be safer not to use it for a portable stamp, as you need to insert something thin through the slit on the side and push it out slowly.
The price of the "Pitatto Seal Stand" is 108 yen (tax included). If you have many opportunities to stamp your seal at home or at work, why not give it a try?