Praise be to Allah.
If the seminar in question is an Islamic or beneficial educational seminar, and the women come wearing complete shar‘i hijab, and there is no free mixing or anything else that is contrary to Islamic teachings, and the men sit in the front rows, and the women sit behind them, in their hijab, at an appropriate distance, and all of them listen to beneficial lectures without free mixing or the women raising their voices, then there is nothing wrong with that, even if there is no screen between the men and women. We have explained this in the answer to question no. 129693
Shaykh Ibn Baaz (may Allah have mercy on him) was asked:
There is a mosque in our city, in which there is a section for the women, that is separated from the men’s mosque by a wall. The women have loudspeakers so that they can hear the imam and the teacher. A man came and wanted to knock down the wall, and his evidence for doing so was the hadith of the Prophet (blessings and peace of Allah be upon him: “The men formed rows, then the children, then the women.” This led to a grave difference of opinion. What do you advise?
There is nothing wrong with any of that. The women at the time of the Prophet (blessings and peace of Allah be upon him) used to pray with the men, behind the men, without a wall, without anything. They covered themselves and wore hijab, and they prayed with the men at the back, as in the saheeh hadith in which the Prophet (blessings and peace of Allah be upon him) said: “The best rows for men are those at the front and the worst are those at the back; the best rows for women are those at the back and the worst are those at the front.” That is because the front rows may be close to the men, but if they pray at the back of the mosque, behind the men, and cover themselves, then there is nothing wrong with it and there is no need for a wall or anything else.
But if a wall is put up, or a curtain instead of a wall, so that the women may feel at ease, and cover their faces and relax, then there is nothing wrong with that, so that they can feel comfortable in their prayer place and they can listen via loudspeakers, or from the imam if they can hear him without a loudspeaker. There is nothing wrong with that. The matter is broad in scope, praise be to Allah.
If they put up a grillwork screen through which they can see the imam or members of the congregation, and hear his voice, there is nothing wrong with that either.
The matter is broad in scope and this harshness is not appropriate. Whether there is a wall or a grillwork screen or a curtain, or none of that, it is fine. All of that is permissible, praise be to Allah. At the time of the Prophet (blessings and peace of Allah be upon him) there was no wall or anything else. They covered themselves and prayed with the people behind the men.
End quote from Fataawa Noor ‘ala ad-Darb (12/267-269)
And Allah knows best.