Hello NHK and welcome. Can you contact the previous owners to find how they worked the Hebs? They are likely to have had a system, and the ewes will be familiar with that. Flapping and chasing will never work with Hebs, quiet confidence will, but that will take time.
There is always one in any flock/group of Hebs, and the other primitives, which will lead the breakaway. Sounds like you have identified yours already
When we have a problem rounding our lot up, for example when there are lambs which are not used to the system, we use a non-electrified electric fence. We make a funnel with this, wide to start, then it narrows to a point at the pen. We build our pen with hurdles - you need hurdles for flexibility - deeper than wide, with a closeable hurdle at the entrance. We walk the sheep in then swing the hurdle across like a gate. Having some food in there first will distract them. If you run them in, they will jump right back out again.
Working on your own is not easy especially when you and your sheep are getting used to each other. You need a helper. people who are used to working with big flocks of amenable sheep tend to flap their arms and shout at them, which scares Hebs into flight so although you might think they would be a help often they are more of a hindrance. Hebs startle very easily as they are independent prey animals which are used to saving themselves.
The method Nimbusllama describes is best achieved gradually. Get the ewes familiar with eating in the pen, making no attempt to catch them or startle them.
Wander quietly off and leave them to it at first so they relax. Next get them used to you standing outside the pen (lean in to put the food in a trough, then you don't have to try to squeeze past them, which will never work). Next get them used to having the gate shut on them, but still don't try to catch them, moving slowly and calmly. This whole process should only take a few days. If you arrange a hurdle pen which you can make smaller once the sheep are in without them escaping while you do it, it makes it much easier to catch them up. Don't handle them by the horns, which hurts them and they will resist. The best way is to put a hand under the chin, and use your leg to press the sheep against the side of the pen. If you put the back end into a corner then when they try to reverse they can't Don't leave it until it is urgent that you catch them, because you will transfer your angst to them. Also, don't have a set of shears visible, nor a strange shearer, don't even walk as if you are about to do something different they're not going to like, even a nonchalant stroll will warn them. being prey animals they can read every nuance of your behaviour.
It sounds impossible, or at least daunting, but you will get there. It's a good idea to wander around in their paddock, or just sit and watch them for a while each day, so they get used to you, what you look like, and how you behave.