One Placing pole, then 3 metres to a cross, then another 7 meters to an oxer as shown below:
This is a good exercise for green horses. Distances between poles may vary depending on the horse natural stride. It should be built progressively along the training. For instance, first place poles on the ground, then the cross, then small vertical and finally the oxer. Maximum height would depend on the horse ability and experience but I wouldn't go bigger than 1.20m maybe 1.30m at the oxer.