There was a time that elders did perform baptisms not waiting until an assembly or convention. Baptized in rivers, lakes, oceans, even a horse trough. People just showed up with the "proper" gear (big robes at one time) No 200 plus questions to go through with 3 elders.
What is the current explanation of "inner rooms"?
*** w09 5/15 p. 8 Where Should You Be When the End Comes? ***In our day, the “interior rooms” of this prophecy could be closely associated with the more than 100,000 congregations of Jehovah’s Witnesses around the world. Such congregations play an important role in our lives. They will continue to do so through “the great tribulation.” (Rev. 7:14) God’s people are commanded to go into their “interior rooms” and hide themselves “until the denunciation passes over.” It is vital that we develop and maintain a wholesome attitude toward the congregation and be firmly resolved to stay in close association with it. We can take to heart Paul’s exhortation: “Let us consider one another to incite to love and fine works, not forsaking the gathering of ourselves together, as some have the custom, but encouraging one another, and all the more so as [we] behold the day drawing near.”—Heb. 10:24, 25.
*** w01 3/1 p. 21 par. 17 Salvation for Those Who Choose the Light ***Today, the “interior rooms” of the prophecylikely have to do with the tens of thousands of congregations of Jehovah’s people around the world. Such congregations are a protection even now, a place where Christians find safety among their brothers, under the loving care of the elders. (Isaiah 32:1, 2; Hebrews 10:24, 25) This is especially true in view of the nearness of the end of this system of things when survival will depend on obedience.—Zephaniah 2:3.
*** w98 8/15 p. 19 par. 14 Strengthening Our Confidence in God’s Righteousness ***In the near future, the greatest time of tribulation ever to strike the human race will break forth suddenly. (Matthew 24:21) When it does, servants of God will need as never before to display confidence in Jehovah’s righteousness and in the direction provided by his organization. In a symbolic way, they will then confidently obey God’s injunction: “Go, my people, enter into your interior rooms, and shut your doors behind you. Hide yourself for but a moment until the denunciation passes over.” (Isaiah 26:20) Already they have entered into the protective atmosphere of over 85,000 congregations in 232 lands. Whatever may additionally be included in the injunction “enter into your interior rooms,” we can be confident that Jehovah will help us to carry it out.
*** w88 1/15 p. 17 par. 8 Trust in Jah Jehovah! ***As Kingdom expansion moves to a climax, Jehovah’s call at Isaiah 26:20 rings forth: “Go, my people, enter into your interior rooms, and shut your doors behind you. Hide yourself for but a moment until the denunciation passes over.” No doubt the “interior rooms” of this prophecy are linked closely with the more than 54,000 citylike congregations that serve Jehovah’s Witnesses throughout the earth today. What Jehovah has in mind remains to be seen. But we can be sure that when he destroys the wicked, he will protect his trusting people, just as he did in Isaiah’s day in turning back the cruel Assyrian.—Isaiah 10:24-26.