Those that are stating that it is O.K. to run a 2 stroke engine without oil are not giving good advice, the whole principle of having oil in the fuel mix is to lubricate the engine components.
The poster being new to biking is asking for advice which is the correct way to carry out work on HIS bike and Oscarthegrouch and KCMC have given this.
Brutale r and Slowlearner, your method is OK for YOUR engines, as if and when, they do fail it is you that has to deal with the engine failure. Brutale r sorry mate but you even state what finally happened to your engine, all right you say it took 2 laps, but at what point did that seizure begin to occur.
I'll tell you, just when the oil ran out. No oil equals no lubrication, no lubrication, engine components begin to fail, it could be instant on an older engine or may take slightly longer on a newer engine but rapid wear is the result otherwise why bother with oil in the first place.
With regard to premix, as KCMC says only put in a small amount, the reason being that when the oil pump does resume pumping oil to the carb the mixture percentage goes up and you could start to suffer high carbon deposits to the piston crown which will break away and foul the spark plug which in turn will cause the engine to stop.
So Jamie95 if I were you I would go with the advice of Oscarthegrouch and KCMC,
assumption is the mother of all f*** ups.