In his tafseer of the verse in Surah al-A'raaf (7:54), "Then He ascended over the Throne", al-Qurtubi says:

Translation of al-Qurtubi's Statement

Most of the past (the early) and later [theologians] said, 'When it is necessary to purify the Creator (al-Baaree), the Sublime, from having direction (jihah) and demarcation (tamayyuz), then from the requirements and necessary consequences of this, in the view of the generality of the past scholars and their later leaders, is to purify the Creator (al-Baaree) from having direction (jihah). In their view, He is not in the direction of above. This is because to them, when Allaah is designated with direction, this would necessitate that He is restricted to a place (makaan) and a confine (hayyiz). (Subsequently), a place and a confine necessitate (for Him) (such) movement and stillness that is related to distinction (tamayyuz), transformation (taghayyur) and new occurrences (Hudooth) . This is the saying of the Theologians (mutakallimoon, the people of kalaam).

And the very first Salaf (may Allaah be pleased with them) never used speak with the negation of direction (al-jihah) and nor did they express that (negation). Rather, they, and all of them, spoke with affirmation of it (al-jihah) for Allaah, the Exalted, just as His Book spoke with it and His Messengers informed of it. And not a single one of the Righteous Predecessors (as-Salaf us-Salih) denied that He ascended over His Throne, in reality (haqeeqatan). And the Throne has been specified (with al-Istiwaa) because it is the greatest of His creations. And they (the Salaf) [stated their] ignorance of the how (kayfiyyah) of al-istiwaa, for there is no one who knows its reality. Imaam Malik said, may Allaah have mercy upon him, "Al-Istiwaa is known..." - meaning, in the language - "...and how (it is) is unknown, and asking about it is an innovation". And Umm Salamah, may Allaah be pleased with her, said the same. And this much is sufficient (on this issue) and whoever wishes more then he can refer to the relevant places in the books of the Scholars.

So it is clear from the above that al-Qurtubi mentions that the way of the Salaf was different to the way of the mutakallimeen (Theologians), and that the Salaf never spoke with what the (later) Theologians spoke with, and they affirmed that Allaah made istiwaa over His Throne in reality (haqeeqatan) - and that they only denied knowledge of how He made istiwaa - and he (al-Qurtubi) brought the saying of Imaam Malik within this context, indicating that the meaning of al-istiwaa is known - and as he (al-Qurtubi) is speaking about the position of the Salaf, when al-Qurtubi says "in the language" when quoting the famous statement of Imaam Malik, then that means that the Salaf understood what istiwaa meant and they affirmed it upon that meaning.

And in this, al-Qurtubi (considered an Ash'ari) is just and fair in that he mentions the unequivocal position of the Salaf and contrasts it to that of the Theologians. And just as clear is what he mentions in his book "al-Asnaa" where he also discusses al-istiwaa, as we have covered in a separate article:

And the translation of which is:

And the most clear of these sayings - even if I do not speak with it or choose it - is what the [Qur'anic] verses and Narrations manifestly (indicate) that Allaah, the Sublime, is above His Throne, just as He informed in His Book and upon the tongue of His Messenger, without asking how, separate and distinct from all of his creation (baa'inun min jamee'i khalqihi). This is the sum of the madhhab of the righteous predecessors (as-salaf as-saalih) in that which the trustworthy narrators (ath-thiqaat) have transmitted from them.

And this is the same as what he said in his tafseer regarding al-istiwaa - that what is apparently manifest in the Book and the Sunnah and what the Salaf were clearly and manifestly upon was that Allaah is separate and distinct from His creation and that He made istiwaa in reality (haqeeqatan) and that He is above the creation.

And all of this is in addition to al-Qurtubi's ascribing to the most prominent amongst the Early Ash'aris (that is Abu Hasan al-Ash'ari himself, and Abu Bakr al-Baqillani and also Ibn Fawrak) the affirmation of Allaah being above His Throne, with His Essence (bi dhaatihi) and that He made istiwaa, in reality (haqeeqatan) as opposed to metaphorically. You can see that article here.