The Shulhan Aruch (Orah Haim 123) writes that after one completes the Amida, and takes three steps backward for "Oseh Shalom," he should stand in place until the Hazan reaches "Nakdishach." The Mishna Berura adds that one should preferably remain standing with his feet together, as he does during the recitation of the Amida. When the Hazan reaches "Nakdishach," one should then take three steps forward, returning to the exact place where he stood while reciting the Amida, and recite "Nakdishach" with the congregation.
The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Teruma (5), citing the Hesed La’alafim (Rav Eliezer Papo, 1785-1828), writes that one should remain standing in place until he answers "Amen" to the Hazan’s recitation of the blessing, "Ha’Kel Ha’kadosh." He may then return to his seat.
Hacham David Yosef (contemporary), in his Halacha Berura (p. 240; listen to audio recording for precise citation), addresses the case of a person who prays without a Minyan, and there is thus no repetition of the Amida and no recitation of "Nakdishach." He writes that after completing the Amida and taking three steps back, the person should, preferably, remain in place for the amount of time he would if he were praying with a Minyan. Meaning, he should remain standing for the amount of time needed for the Hazan to recite the first three blessings of the Amida, until "Nakdishach" (approximately 45 seconds), and then take three steps forward. Strictly speaking, however, it suffices to remain in place for the amount of time needed to walk four Amot (6-8 feet).
Hacham David notes that this applies also to a person praying with a Minyan who does not complete the Amida by the time the Hazan reaches "Nakdishach." Since this person will not be reciting "Nakdishach" after completing his Amida, he should remain in place for the amount of time mentioned above, and then take three steps forward.
Summary: After one completes the Amida and takes three steps back, he should remain in place until the Hazan reaches "Nakdishach," and then take three steps forward, to the place where he had recited the Amida. He should remain there until he recites "Amen" to the blessing of "Ha’Kel Ha’kadosh." If one prays without a Minyan, or if he completes the Amida after the congregation recited "Nakdishach," then after taking three steps backward he should, preferably, remain in place for the amount of time it takes the Hazan to recite the first part of the Amida, until "Nakdishach." Strictly speaking, it suffices to wait only the amount of time needed to walk four Amot.
