The spider Agroeca brunnea makes a simple-looking egg sac and usually attaches it to an elevated site. But the curious thing is that it is bicameral, composed by the chamber of the eggs (1) and the chamber of molt (2).
Eggs hatch in chamber 1 and newborn spiders pierce the cover plate, falling into chamber 2. They remain there for 2-3 weeks until they make their first molt. After this, they are more independent, so they break that chamber and go outside. We could really talk about a shelter for newborn and invalid spiders during their first few weeks of life.