Address review comments

builder/oracle/oci/config.go

@@ -283,6 +283,18 @@ func (c *Config) Prepare(raws ...interface{}) error {
 			errs, errors.New("'shape' must be specified"))
 	}
 
+	if strings.HasSuffix(c.Shape, "Flex") {
+		if c.ShapeConfig.Ocpus == nil {
+			errs = packersdk.MultiErrorAppend(
+				errs, errors.New("'Ocpus' must be specified when using flexible shapes"))
+		}
+	}
+
+	if c.ShapeConfig.MemoryInGBs != nil && c.ShapeConfig.Ocpus == nil {
+		errs = packersdk.MultiErrorAppend(
+			errs, errors.New("'Ocpus' must be specified if memory_in_gbs is specified"))
+	}
+
 	if (c.SubnetID == "") && (c.CreateVnicDetails.SubnetId == nil) {
 		errs = packersdk.MultiErrorAppend(
 			errs, errors.New("'subnet_ocid' must be specified"))

builder/oracle/oci/driver_oci.go

@@ -95,11 +95,6 @@ func (d *driverOCI) CreateInstance(ctx context.Context, publicKey string) (strin
 		FreeformTags:        d.cfg.CreateVnicDetails.FreeformTags,
 	}
 
-	LaunchInstanceShapeConfigDetails := core.LaunchInstanceShapeConfigDetails{
-		Ocpus:       d.cfg.ShapeConfig.Ocpus,
-		MemoryInGBs: d.cfg.ShapeConfig.MemoryInGBs,
-	}
-
 	// Determine base image ID
 	var imageId *string
 	if d.cfg.BaseImageID != "" {
@@ -159,11 +154,18 @@ func (d *driverOCI) CreateInstance(ctx context.Context, publicKey string) (strin
 		DisplayName:        d.cfg.InstanceName,
 		FreeformTags:       d.cfg.InstanceTags,
 		Shape:              &d.cfg.Shape,
-		ShapeConfig:        &LaunchInstanceShapeConfigDetails,
 		SourceDetails:      InstanceSourceDetails,
 		Metadata:           metadata,
 	}
 
+	if d.cfg.ShapeConfig.Ocpus != nil {
+		LaunchInstanceShapeConfigDetails := core.LaunchInstanceShapeConfigDetails{
+			Ocpus:       d.cfg.ShapeConfig.Ocpus,
+			MemoryInGBs: d.cfg.ShapeConfig.MemoryInGBs,
+		}
+		instanceDetails.ShapeConfig = &LaunchInstanceShapeConfigDetails
+	}
+
 	instance, err := d.computeClient.LaunchInstance(context.TODO(), core.LaunchInstanceRequest{
 		LaunchInstanceDetails: instanceDetails,
 		RequestMetadata:       requestMetadata,

website/content/docs/builders/oracle/oci.mdx

@@ -100,10 +100,7 @@ can also be supplied to override the typical auto-generated key:
   [ListShapes](https://docs.us-phoenix-1.oraclecloud.com/api/#/en/iaas/20160918/Shape/ListShapes)
   operation available in the Core Services API.
 
-- `shape_config` (map of strings) - The shape configuration for an instance. The shape configuration determines the resources 
+  When using flexible shapes, ocpus must be set.
-  allocated to an instance. Options:
-  - `ocpus` - The total number of OCPUs available to the instance.
-  - `memory_in_gbs` - The total amount of memory, in gigabytes, available to the instance.
 
 - `subnet_ocid` (string) - The name of the subnet within which a new instance
   is launched and provisioned.
@@ -192,6 +189,11 @@ can also be supplied to override the typical auto-generated key:
 - `use_private_ip` (boolean) - Use private ip addresses to connect to the
   instance via ssh.
 
+- `shape_config` (object) - The shape configuration for an instance. The shape configuration determines the resources 
+  allocated to an instance. Options:
+  - `ocpus` (required when using flexible shapes or memory_in_gbs is set) (float32) - The total number of OCPUs available to the instance.
+  - `memory_in_gbs` (optional) (float32) - The total amount of memory, in gigabytes, available to the instance.
+
 <!-- markdown-link-check-disable -->
 - `metadata` (map of strings) - Metadata optionally contains custom metadata
   key/value pairs provided in the configuration. While this can be used to